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Sudhir Vempati
IISc
Rare Processes
April 5, 2019, Friday
04:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
The discovery of neutrino masses and mixing has raised important theoretical challenges due to their tiny masses and large mixing angles. Generating such tiny couplings would typically require special mechanisms like, suppressing by a large mass scale or by a (extra space dimensional) volume etc. When these are put together in larger theoretical frameworks which solve the hierarchy problem, it has interesting consequences: large rates for rare decays like \mu \to e + \gamma, or \tau \to mu + \gamma etc. In the coming years, new experiments will be searching for these rare decays with a precision orders of magnitude beyond the current limit. We consider three example frameworks including the recently proposed clockwork mechanism and discuss the strong implications these processes have on the theoretical models.
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Sampat Raj Vadera
IIT Jodhpur
Functional Electromagnetic Materials for Camouflage and Stealth
Applications
March 29, 2019, Friday
04:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
With the advancements in sensors, computational and communication technologies, the survival of military resources has become one of the major challenges for the Armed Forces across the world. The imaging sensors operating over a wide range of electromagnetic spectrum, from visible-near infrared to microwaves and millimeter waves, coupled with real time processing technologies has rendered the military equipment highly vulnerable to precision strike by the enemy. These advancements in sensor technologies require matching developments in the area of camouflage and stealth technologies which can defy the detection and identification of military targets by the adversary. Materials with desired electromagnetic properties are very important components of camouflage and stealth technologies. The major challenge before the scientific community to develop materials or materials combinations which can address the requirements covering a very wide range of wavelengths of operating sensors. In this talk, I shall present basic concepts of camouflage and stealth together with the materials research done by our group in this area.
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Jim Libby
IIT Madras
Belle II: flavour physics at the intensity frontier
March 15, 2019, Friday
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
On April 26th 2018 the SuperKEKB e+e- accelerator produced its first collisions, which were recorded by the Belle II detector. SuperKEKB is the first new particle accelerator to begin operation since the LHC. SuperKEKB is an intensity-frontier machine that is designed to reach an instantaneous luminosity of 8 x 10^35 cm^-2s^-1. Operating at a centre-of-mass energy corresponding to the peak of the Upsilon(4S) resonance, the goal is accumulate a data sample corresponding to an integrated luminosity of 50 ab^-1. The sample will contain billions of B mesons, charm hadrons and tau leptons that the Belle II experiment will use to search for rare decays and perform precision measurements of flavour observables. These searches and measurements allow indirect probes of physics beyond the standard model. This talk will first motivate the Belle II physics programme, before describing SuperKEKB and the Belle II experiment. Results from the 2018 pilot run, along with specific examples of the physics potential related to tests of lepton-universality and measurements of the Unitarity Triangle will be presented. Throughout, the complementarity and competition with LHCb and its upgrades will be noted.
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Anurag Gupta
IIT Kanpur
Acoustical Perspectives on Indian Musical Instruments
March 8, 2019, Friday
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
We will discuss several unique design features in Indian musical instruments from an acoustical viewpoint. First, we will look at a variety of Indian drums - tabla, pakhawaj, idakka - all of which are adept in producing melody. Using simple mathematical models we will illustrate how these drums are capable of producing sound which is rich in overtones and therefore transmit definite pitch. Second, we will make an attempt to understand the complex structure of tanpura sound in light of our recent experimental and theoretical investigations. Our focus will be to investigate the acoustic signature behind the distinctiveness of tanpura’s drone. Throughout, we will discuss historical contexts of our work and also explore several avenues for research.
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K. P. Rajeev
IIT Kanpur
Low Energy Nuclear Reactions: Time for a Paradigm Shift in Physics?
March 1, 2019, Friday
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
There have been several experimental observations, over the course of a century or so, where transmutation of elements have been found to happen in table top experiments that does not make use of high energy particles. According to our current understanding of Physics such phenomena should not happen. We will review some of the important experimental observations starting with the (in)famous experiment conducted by Pons and Fleischmann and dubbed as “Cold Fusion” and dismissed by the mainstream physics community as “pathological science”. The field has since been renamed as Low Energy Nuclear Reactions (LENR) though it still carries some of the old stigma. This colloquium is an attempt to assess the current situation and its implications for science and technology. The talk will also present some of the speaker’s own attempts to verify some of the claims of this field. Also, some of the recent technological developments and the tantalizing possibilities they open up will be touched upon.
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Alok Laddha
Chennai Mathematical Institute
Classical Limit of Soft Graviton Theorem and the memory effect
February 26, 2019, Tuesday
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
In this talk we will show how certain results in Quantum Gravity can be used for analysing low frequency gravitational radiation in classical scattering processes in arbitrary dimensions. In Four dimensions this analysis yields an interesting observable effect. Namely, a late time component in Gravitational field that falls off as inverse power of time, which can be interpreted as a tail term to the Linear Memory effect.
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Dipankar Chakrabarti
IIT Kanpur
Lattice Gauge Theory With Minimally Doubled Fermion
15th February, 2019(Friday)
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Lattice gauge theory is a non-perturbative quantum field theory technique where the space and time are discretized on a four dimensional hypercubic lattice. Though it is successful in calculating many interesting non-perturbative observables, putting fermion on a discrete space-time lattice is difficult due to presence of extra unphysical degrees of freedom, known as "doublers". In 4-dimensions, 15 such doublers appear along with the physical fermion. A no-go theorem implies we need to break chiral symmetry on the lattice to remove these doublers. In minimally doubled fermion formulation, there is only one doubler with chiral symmetry, the minimum number allowed by the "no-go" theorem. But the minimally double fermions break parity and time reversal invariances and so people are skeptic about using them. In this talk I will discuss one such minimally doubled fermion formulation to show how these invariances can be restored and demonstrate that it can be used to investigate interesting nonperturbative physics.
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Durgesh Tripathi
The Inter-University Centre for Astronomy and Astrophysics(IUCAA)
Heating and Dynamics of Sun's Atmosphere
8th February, 2019(Friday)
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
The Sun is the closest star that not only shapes the environment we live in but also challenge our physical understanding of the working of the star. On the one hand, the Sun's UV and X-ray radiation do impact the dynamics of the Earth's atmosphere. On the other hand, the existence of million-degree hot corona (atmosphere) above mere 6000 K photosphere (surface) and dynamics therein at a range of spatial and temporal scales has been considered to be one of the most stubborn problems in Astrophysics, since its discovery in 1940. Besides, the high energy explosions on the Sun affects the space weather and can have devastating effects on society. In this talk, I shall focus primarily on the heating and dynamics of the active solar regions which demonstrate the most pronounced form of coronal heating and dynamics and they also form the source regions of high energy explosions. I shall provide a brief overview of the field including the open questions followed by some recent results obtained using the observations recorded with the state-of-the-art current space missions.
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Avinash Deshpande
Raman Research Institute(RRI)
On the Attempts to Detect the Global Spectral Signature of the Cosmic
Dawn
1st February, 2019(Friday)
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
A number of on-going and planned future efforts at low radio frequencies aim to detect precious tokens of the yet unobserved details of the transition from the dark ages to the cosmic dawn and beyond to completion of reionization, heralded by the first stars. The potential detectability of global signal from the red-shifted 21-cm line of atomic hydrogen across this cosmic transition was first discussed by Shaver et al. (1999). Detection of such signals holds unmatched promise to reveal several key details of the physical condition and constituents of the universe during these early epochs. However, the associated challenges are not confined only to isolating the weak signal of interest from the orders of magnitude brighter foregrounds, but extend equally to reliably establishing the origin of the apparent global signal to the very early epochs.
The talk will highlight the challenges in such measurements and the attempts so far to detect the global signal, including the recently claimed "detection of a flattened absorption profile in the sky-averaged radio spectrum". by Bowman et al (2018). The potential of a novel model-independent path toward isolating the foreground contribution will be discussed, and a critical test that the measurements of the global cosmic-dawn signal should necessarily pass will be presented.
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Anirban Chakraborti
Jawaharlal Nehru University
Predicting the unpredictable: A case study of financial market crashes
25th January, 2019(Friday)
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Catastrophic events, though rare, do occur and when they occur, they have devastating effects. The study of the critical dynamics in complex systems is always interesting yet challenging. First, we present a brief overview of the random matrix theory and correlated Wishart ensemble. Then, we choose financial market as an example of a complex system, and do the analysis of the S&P 500 (USA) stock market based on the evolution of cross-correlation structure patterns. We identify “market states” as clusters of similar correlation structures, which occur more frequently than by pure chance (randomness). Power mapping method from the random matrix theory is used to suppress the noise on correlation patterns, and an adaptation of the intra-cluster distance method is used to obtain the optimum number of market states, and also identify the “precursors” to the crashes. The dynamics of the transitions between the states are interesting. Further, the resulting “emerging spectrum” of eigenvalues near zero, have intriguing properties: (i) the shape of the emerging spectrum reflects the market instability, (ii) the smallest eigenvalue is able to statistically distinguish the nature of a market crash or crisis. We finally investigate whether the smallest eigenvalue is able to predict a high market correlation, which is a signature of a crash.
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Saikat Ghosh
IIT KANPUR
Superposed states of atoms and nano-mechanical resonators
18th January, 2019(Friday)
5:00 pm (Tea at 4.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
We will discuss some recent results on two experiments in our lab: on atoms and on 2-dimensional (graphene) mechanical resonators. In particular, we will describe a single-shot measure of quantum coherence in atoms, that accurately quantifies superposed states in experimentally simulated open and closed thermal ensembles. Furthermore, we find that the measure can be applied to freeze such superposed states, countering incoherent decay. We will also discuss a mechanical amplifier that we have developed using few-atomic layer graphene, which can measure displacements down to 3.4 femto-meter, integrated over a second. We use parametric squeezing to reach these extreme scales. The system also displays a range of rich non-linearity, including phonon lasing, cooling, phase coherent phononic frequency combs and can induce giant non-linearity in an otherwise linear, NEMS oscillator. We will end with a discussion on our future experiments towards integrating these two powerful but otherwise disconnected platforms of atoms and 2-dimensional mechanical resonators and probable benefits of undertaking such an exercise.
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Tapobrata Sarkar
IIT KANPUR
Small Anisotropy in Stellar Objects in Modified Theories of Gravity
11th January, 2019(Friday)
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Interior structures of stellar objects might have small pressure anisotropy due to several reasons. In this talk, we will review this, and study the possible role of small anisotropy in stellar interiors in theories of modified gravity, that are known to alter the hydrostatic equilibrium condition inside stars. We will discuss how anisotropy may put lower and upper bounds on the modified gravity parameter depending on the polytropic equation of state. We will also discuss the mass of stellar objects in these theories, and the associated modification of the Chandrasekhar mass limit in white dwarf stars. Effects of small pressure anisotropy on the Hydrogen burning limit in low mass stars will be commented upon.
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Arjun Bagchi
IIT KANPUR
Towards Realistic Holography
4th January, 2019(Friday)
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
The Holographic Principle is mainly understood for negatively curved Anti-de Sitter spacetimes, through the celebrated AdS/CFT correspondence. Our universe is clearly not AdS and hence we need to generalise the notion of holography beyond AdS. In this talk, I would outline some steps towards construction of holography for asymptotically flat spacetimes. The later half of the talk would be focused on more technical recent developments, viz. modified modular invariance and the construction of characters of the underlying symmetry algebra.
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Pankaj Joshi
Institut Néel, Univ. Grenoble Alpes, Grenoble INP and CNRS
Black Holes and Quantum Stars: Observer's Paradise?
12th November, Monday, 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Einstein's theory of gravity predicts the existence of Black Holes and Space-time Singularities. We discuss the current efforts to make a direct observational detection of these entities. The Black Holes and visible or Naked Singularities arise from the gravitational collapse of massive stars. Quantum gravity effects dominate near the naked singularities, that we may call `Quantum Stars', which may be long or short lived. These offer an opportunity to test the quantum theories of gravity, or the Unification of Physics. The connection to new observational missions such as the Event Horizon Telescope, Gravitational Waves, TMT, and others are pointed out and exciting theoretical developments emerging are indicated.
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Hervé Courtois
Institut Néel, Univ. Grenoble Alpes, Grenoble INP and CNRS
Quantum Thermodynamics in a Single Electron Transistor
9th November, Friday, 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Single Electron Transistors (SETs) are key elements of quantum nano-electronics. Investigating their thermodynamic properties is thus of both fundamental and practical interest. In this talk, I will review our recent experiments on the thermal conductance and the thermo-power of SETs. Devices based on either a metallic island or a quantum dot are investigated. In particular, I will discuss the violation of the celebrated Wiedemann-Franz (relating the thermal conductance and the electrical conductance) in a metallic SET. In a quantum dot strongly coupled to one lead, the Kondo effect generates a peak in the tunneling density of states close to the Fermi level. I will report on measurements of the thermo-power, showing that this Kondo peak is shifted from the Fermi level.
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Palash Baran Pal
SINP, Kolkata
Quantum Synchronisation in the Quantum Regime
2nd November, Friday, 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
I will discuss, starting from Newtonian times, how physicists have tried to understand different forces in a single unified framework. The pursuit includes Maxwell's unification of electricity and magnetism, and modern gauge theories of interaction, leading to the idea of grand unification.
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Mahendra Verma
IIT Kanpur
Description of nature: A single law or many laws?
25th October, Thursday, 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
To understand nature, physicists have attempted to construct minimalistic laws to describe varied phenomena. In history of science, there have been successes in this direction — Maxwell’s unification, unification of forces, etc. However, the world appears to be quite complex, and there is a school that believe that not everything can be reduced to a single framework. For example, phase transition is described by large-scale modes. Turbulent flows have their own framework, and possibly it cannot be derived from first principle. It is possible that different layers of nature have their own laws, thus nature’s laws may be hierarchical.
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Sai Vinjanampathy
IIT Bombay
Quantum Synchronisation in the Quantum Regime
12th October, Friday, 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
It is well known that weakly coupled, self-sustained oscillators can mutually lock the phase of their oscillations in classical mechanics. Such a phenomenon is known as synchronisation. Given the experimental progress of seeing resonators in the quantum regime, there is an ongoing effort to observe synchronisation and other non-linear dynamical effects in quantum systems. It is desirable to observe such synchronisation of quantum systems not just in the classical regime, but also in the quantum regime. This quantum regime is defined by low number of excitations and a highly non-classical steady state of the self-sustained oscillator. In this talk, I will introduce quantum synchronisation and present several results relating to the synchronisation of quantum systems. I will also comment on the applications of these new ideas to quantum technologies All interested are welcome.
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D. S. Rana
IISER, Bhopal
Terahertz Science and Technology in Condensed Matter
5th October, Friday, 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Terahertz (THz) science and technology has proved its potential to unravel novel phases and functionality in a wide range of condensed matter systems of contemporary interest. In electronic and magnetic complex systems, the study of low energy (0.5-20 meV) dynamics/excitations using THz time-domain and of ultrafast functionality employing THz emission spectroscopy explores those novel electronics phases and ground states which are beyond the scope of static and low frequency transport property determination techniques. Such studies when performed on high quality epitaxial thin films can probe both the collective excitations/dynamics of ordered electronic phases and the free carriers’ dynamics under the influence of THz electric fields. In this talk, I’ll present some of our recent THz spectroscopic investigations on coherently strained thin films of complex perovskite nickelates which are known to exhibit inter-related electronic, magnetic and structural phase transition via complex interplay of competing energetics of spin, charge, lattice and orbitals. Our studies reveal a variety of low energy carrier dynamics such as resonance absorption by charge-density-wave type excitations, non-Drude type of conductivity, non-Fermi liquid behavior, etc. These studies resolve some long standing issues pertinent to phase-diagram of nickelates.
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Kavita Jain
JNCASR, Bangalore
How fast does a biological population adapt?
28th September, Thursday, 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
In an influential essay, evolutionary biologist Theo Dobzhansky stated that “nothing in biology makes sense except in the light of evolution”. Indeed, evolution shapes diversity at all levels of biological organization, ranging from cells to species. Population genetics and quantitative genetics have been used for over a century to understand biological evolution, and share many ideas with statistical physics and thermodynamics. In this talk, I will introduce some basic population-genetic concepts, and processes that drive biological evolution. I will then describe our recent theoretical results on the adaptation dynamics of populations in static and continually changing environments, and their relation to microbial experiments.
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Rajeev Gupta
IIT Kanpur
Quest for a Room Temperature Multiferroic
25th September, Thursday, 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Multiferroic materials have attracted enormous interest in recent times due to their perceived potential applications such as in sensors, actuators and memory devices. This phenomenon seldom occurs in nature-generated materials near room temperature. Therefore, it is vital to explore new lab synthesized multiferroic materials demonstrating the multiferroic effect near or above room temperature. In this talk, we will discuss our results on two materials – Gallium Ferrite and Yttrium Orthoferrite (YCrO3).
Gallium ferrite (GaFeO3 or GFO) is a low temperature ferrimagnet and room temperature piezoelectric wherein the magnetic transition temperature can be tailored to room temperature and above by tuning the stoichiometry. We have systematically studied the evolution of phonons in good quality samples of GFO using Raman spectroscopy. Using the phonon softening behavior and nearest neighbor spin-spin correlation function we estimated spin-phonon coupling strength in the magnetically ordered state. We also show, for the first time, the presence of a spin glass phase in GFO where the spin-glass transition has a signature of abrupt change in the spin-phonon coupling strength. We also demonstrate room temperature ferroelectricity in epitaxial thin films of gallium ferrite.
Next, we use the example of YCrO3 to show that there are two competing phenomenon – onset of ferroelectricity due to rotation of CrO6 octahedra and displacement of Y atom leading to suppression of ferroelectricity. This competition reveals that while the octahedral rotations favor a lower symmetry state, the Y atom displacement opposes it, leaving YCrO3 to exhibit only an incipient ferroelectric state. The evolution of phonon modes supports the role of phonons in the origin of ferroelectricity associated with the local distortion in the crystal structure. We believe that this work addresses the long-standing question as to why, despite the high temperature perovskite cubic structure being so common, very few oxides transform into the R3c structure and exhibit ferroelectricity.
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V Subrahmanyam
IIT Kanpur
Entanglement in Spin systems: Distribution, Generation, Nonlocal Bell Pairs
24th September, Thursday, 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Quantum entanglement is recognised, in recent years, as a resource in information processing and communication protocols. Many-electron spin states can exhibit a variety of entanglement structure. The entanglement can be redistributed and generated when the system undergoes a dynamical process. We will discuss the distribution and generation of multi-partite entanglement through a Hamiltonian evolution of initial unentangled spin states, for well-known quantum spin models. A quantum circuit will be presented that uses the dynamics of a kicked transverse field Ising model, that generates a multi-party entanglement structure, and non local Bell pairs.
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Anjan K. Gupta
IIT Kanpur
Strengthening the superconducting weak-links in m-SQUIDs for probing nano-magnetism
20th September, Thursday, 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Nano-magnetism is of interest for the underlying physics as well as applications. Magnetic measurements of an individual magnetic nano-particle, as compared to an ensemble, are preferred as they avoid complications arising from averaging over particle size and shape as well their interactions. Magnetometry using micron-size superconducting quantum interference devices (m-SQUIDs) has been remarkably successful in probing classical as well as quantum regimes of magnetism in single particles. This technique can be further improved for better speed and higher sensitivity with hysteresis-free m-SQUIDs. The later has been a challenge, particularly at low temperatures, which is essential for probing quantum-magnetism. The hysteresis in these devices arises from thermal instabilities in superconducting weak-links that are used as Josephson junctions in m-SQUIDs. The heat generated by resistive normal region leads to a self sustained hot-spot. This has been modeled by solving steady state thermal conduction equation, which is valid in certain regime. However, as we approach the hysteresis-free regime by optimizing the heat evacuation, another regime of hysteresis is found in which the bistability results due to a dynamic steady state. This dynamic regime appears to be more challenging in terms of eliminating hysteresis. The common idea of resistive shunting, which works well in usual tunnel junction based SQUIDs, leads to a marked reduction in sensitivity. By understanding this new regime through a simple model we have been able to device ways of eliminating hysteresis with remarkable sensitivity. We shall also discuss some of the limitations of the model including the non-equilibrium effects. In particular, we find a very slow relaxation of quasi-particles (QPs) that are generated during phase-slips in our devices. This slow relaxation of QPs is known to be a bottleneck in several superconducting devices such as nano-coolers and superconducting qubits.
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Sudip Sengupta
Institute for Plasma Research (IPR), Gandhinagar
On Wave Breaking of Relativistically Intense Longitudinal Space Charge Waves in Plasma
14th September, Friday, 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Spatio-temporal evolution of large amplitude relativistically intense longitudinal space charge waves in plasma is a fascinating fi eld of research. It is not only a topic of fundamental academic interest to nonlinear plasma theory but also serves as a useful paradigm to illustrate the under-lying physics of many plasma based phenomenon in the laboratory and astrophysical scenarios where large amplitude nonlinear space charge waves are excited. A space charge wave is said to be relativistically intense when the energy gained by an electron over a distance of one wavelength becomes of the order or more than its rest mass energy. The amplitude of these nonlinear plasma waves is limited by a phenomenon called wave breaking, which may be induced by several physical processes. In this talk, along with a brief overview, current understanding of wave breaking of relativistically intense space charge waves will be presented. Its application to the rapidly developing field of plasma based particle acceleration schemes will also be touched upon.
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Amita Das
Institute for Plasma Research (IPR), Gandhinagar
Electron Beam Transport in Plasmas
7th September, Friday, 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
The electron beam transport and its energy deposition in plasma is crucial in the context of many applications such as fast ignition etc., where it is desirable to dump energy in an overdense compressed core of the target where lasers are unable to penetrate. The talk will cover complex collective physics associated with electron beam plasma instabilities, the associated evolution of magnetic fields and the ensuing turbulence leading to possible anomalous behavior of transport. The experimental evidences in support of anomalous transport will be provided. A novel effect arising due to finite transverse beam size will also be demonstrated.
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Tarun Kanti Ghosh
IIT Kanpur
Exotic properties of generalized Dirac-Weyl systems
31st August, (Friday), 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
The signatures of Dirac physics in condensed matter systems have been established after the realization of graphene monolayers. In this talk, we will consider two different kinds of 2D Dirac-Weyl systems, namely borophene/deformed graphene having tilted anisotropic Dirac cones and alpha-T3 optical lattice having Dirac cones along with a flat band. We will discuss effect of the tilted anisotropic Dirac cones on zero-momentum optical conductivity of borophene/deformed graphene. The role of a variable Berry phase in magnetotransport coefficients and various properties of Floquet quasienergy states of the alpha-T3 systems will be discussed.
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Dhrubaditya Mitra
NORDITA, Stockholm
Our turbulent times
03rd August, (Friday), 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Turbulence is often called the last unsolved problem of classical physics although it is not always clear what exactly the "problem of turbulence" is. I shall first try to well-define the problem of turbulence from the point of view of a physicist. The common perception of turbulence is a behaviour that changes dramatically over time. I shall show several ways in which to quantify and then understand the dynamic behaviour of a turbulent fluid generalising ideas from statistical mechanics. They are all attempts to precisely define and understand a commonly asked question in turbulence: "What is the lifetime of a turbulent eddy ? ". First by borrowing ideas from dynamical scaling of critical phenomenon and generalising them to dynamical multiscaling in turbulence. Next by numerically calculating the probability distribution of first-passage-times. To cut a long story short, there no unique time scale that corresponds to a particular length scale in a turbulent fluid. Depending on precisely how you define your time scale you will get a different answer. This aspect of turbulence has been elucidated by research done over last two decades.
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Prof. Kedar Khare
Indian Institute of Technology, Delhi
Hilbert Transform in 2D, Complementary Diffraction and Robust Laser Beam Engineering
18th April, (Wednesday), 2018
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Sine and cosine quadratures connected by the Hilbert transform are commonly used in the complex signal representation of optical wavefields. A curious theorem due to L. Mandel (published in 1967) tells us that the quadrature representation obtained via Hilbert transform is the most efficient one in the sense that it leads to a least fluctuating complex signal. I will begin my talk by generalizing Mandel's theorem and showing that the quadrature transform operation for a 2-dimensional signal involves Fourier domain filtering of the 2D signal by a spiral phase function. This result can be tested by a simple laboratory experiment where we observe that when an arbitrary amplitude-phase aperture is illuminated by l = 0 and l = 1 orbital angular momentum (OAM) states, the corresponding far field diffraction intensity patterns are complementary. I will describe two interesting applications of the complementary diffraction phenomenon: (1) spiral phase diversity imaging, (2) engineering of laser beams capable of maintaining robust intensity profile on propagation through random time-varying phase fluctuations as in atmospheric turbulence.
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Prof. Prabal K Maiti
Indian Institute of Science, Bangalore
Modelling complex soft and biomaterials
3rd April, (Tuesday)
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Computer simulations are becoming, or are already, important scientific tools to understand the emergence of collective properties from chemical structures in complex molecular systems. It has helped us in improving our basic understanding of soft and biomaterials and providing calculation tools for the pre-synthesis design and screening of novel materials for various technologies. In this talk I will summarize our efforts in understanding the structure and dynamics, the self-assembly and phase behavior in a number of different soft-matter systems like: DNA, dendrimer, DNA-dendrimer complex, HIV protein and confined water. I will present results from our atomic level simulations on the DNA and dendrimer systems. Using Molecular dynamics (MD) simulations we have been able to study and predict the structural properties of various DNA molecules, which are useful for nanoscale applications. Our atomistic simulations of dendrimer systems allow us to study in great detail various properties of such systems. We have also used MD techniques to study the complex dissociation pathway of protein complex in the context of HIV infection and inhibition. If time permits, I will also talk about modeling effort understanding charge transport in DNA.
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Prof. Anil Shaji
Indian Institute of Science Education and Research, Thiruvananthapuram
NonClassical correlations in quantum information processing and open quantum dynamics
28th March, 2018 (Wednesday)
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
NonClassical correlations in quantum states appear to have a role to play in both quantum information processing as well as in the dynamics of open quantum systems. Quite a bit of literature exists on quantum entanglement, its uses, roles etc. However nonClassical correlations that can be present in a quantum state are not necessarily limited to entanglement have received attention only relatively recently. These other nonClassical features, as quantified by a multitude of proposed measures like discord and measurement induced disturbance, and their role in mixed state quantum computing as well as open quantum dynamics are only beginning to be understood. I present a brief overview of these areas and describe how such correlations can be harnessed to perform useful tasks using appropriate quantum technologies. All interested are welcome.
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Prof. Anirban Sain
Indian Institute of Technology Bombay
Self organised patterns in biological soft matter
22nd March, 2018 (Thursday)
5:00 pm (Tea at 4.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Living organisms form patterns at various length scales, from cells to tissues and organs, all the way up to the full organism level. To understand how these patterns form and function one must study the properties of polymers, membranes, viscous fluids, the so called soft matter, which constitute the cells. Much of the polymers in the cell are short filaments, which often form networks. Recently, physics of liquid crystals have been very useful in interpreting collective behavior of these filaments. Even cell colonies have been interpreted as liquid crystals, which are essentially assembly of many rod like molecules. Liquid crystals, otherwise known for their spectacular visual effects, are already important in technology (e.g., LCD screens). They are well known for the variety of ordered states, which they exhibit, namely nematics, smectics, cholesterics etc. Interestingly, these states are also accompanied by topological defects, and in the biological context the defects have important functional role, and therefore have received more highlight than the ordered states themselves. In this context, I will also discuss some of our research on, a) filament induced spontaneous tubulation of membrane vesicles, and b) pattern of domains which form during crystallisation of colloidal membranes. a) https://arxiv.org/abs/1802.08608, b) https://www.nature.com/articles/s41467-017-01441-3, c) https://physicstoday.scitation.org/doi/full/10.1063/PT.3.3580
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Prof. Anjan Barman
S. N. Bose National Centre for Basic Sciences, Kolkata
Ultrafast Spin Dynamics in Ferromagnetic Thin Films and Nanostructures for Applications in Spintronics and Magnonics
16th March, 2018 (Friday)
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Spintronics and Magnonics are rapidly emerging fields with huge potential applications in magnetic storage, memory, logic, microwave source and data communication devices, and for them to become viable and sustainable technology it is imperative to study excitation, manipulation and detection of spin dynamics in artificially structured materials. Here, we present three different methods of excitation and detection of spin dynamics in ferromagnetic thin films, multilayers, heterostructures and two-dimensional arrays of nanostructures. Optical, thermal and electrical excitation and detection of spin waves in artificial two-dimensional, pseudo-one-dimensional and quasi-periodic ferromagnetic nanodot and nanoantidot lattices will be presented by time-resolved MOKE microscope[1], Brillouin light scattering and ferromagnetic resonance spectroscopy. Investigation and control of collective spin-wave spectrum and Gilbert damping behaviour by varying the physical and material parameters of the magnonic crystals and bias magnetic field will be discussed [2-7]. Important observations such as ultrafast demagnetization, magnonic-mode splitting [2], bandgap formation[5,6], tunability of bandgap[5], dynamic dephasing[2], tunability of inter-element interaction [3,4,7] and transition from collective to non-collective dynamics2 will be discussed based upon experimental data and numerical simulations. A novel all-optical method of investigating spin-Hall effect in heavy metal will be presented [8,9]. Finally, detection of pure interfacial Dzyaloshinskii-Moriya interaction in heterostructures with broken inversion symmetry by Brillouin light scattering measurement will be presented [10,11]. References 1. A. Barman and A. Haldar, Solid State Physics 65, 1-108 (2014). 2. B. Rana et al., ACS Nano, 5, 9559 (2011). 3. R. Mandal et al., ACS Nano 6, 3397 (2012). 4. S. Choudhury et al., ACS Nano 11, 8894 (2017) 5. C. Banerjee et al., Phys. Rev. Applied 8, 014036 (2017). 6. C. Banerjee et al., Phys. Rev. B 96, 024401 (2017). 7. S. Saha et al., Adv. Funct. Mater. 23, 2378 (2013). 8. A. Ganguly et al., Appl. Phys. Lett. 105, 112409 (2014). 9. S. Mondal et al., Phys. Rev. B 96, 054414 (2017). 10. A. K. Chaurasiya et al., Sci. Rep. 6, 32592 (2016). 11. A. K. Chaurasiya et al., Phys. Rev. Applied 9, 014008 (2018).
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Prof. Sibaji Raha
Physics and Environmental Sciences, Bose Institute, Kolkata, INDIA
CLIMATE CHANGE: A PHYSICIST’S PERSPECTIVE
9th March, 2018 (Friday)
4:00 pm (Tea at 3.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Climate Change is, arguably, the greatest challenge facing the human civilisation today. Global warming is a prominent feature, though not the only one, of climate change, which threatens life as we know it today. Internationally, there is a lot of scientific activity aimed at understanding various features of climate change, with the objective of devising workable strategies for alleviation and/or mitigation of its ravages. Most of these studies, however, are empirical in nature. The basic scientific processes, chemical and physical, remain largely unexplored. Till date, only one Nobel Prize has ever been awarded, to Paul Crutzen, Mario Molina and F. Sherwood Rowland in Chemistry (1995), for their work on ozone formation and decomposition in the atmosphere. The realisation that a complete understanding of the issues related to global change requires a better understanding of fundamental processes has dawned only lately. In this semi-technical (almost non-technical) talk, some of the physics issues related to climate change will be highlighted and current approaches to address them will be discussed.
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Prof. Debajyoti Choudhury
Department of Physics & Astrophysics, Delhi University
Top @25
16th February, 2018 (Friday)
5:00 pm (Tea at 4.50 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
Nearly a quarter century after its discovery, the top quark continues to intrigue us. It's role in the understanding of electroweak symmetry breaking (Higgs physics) in particular, and physics beyond the Standard Model cannot be underestimated. In this talk, I will touch upon some of these issues, with emphasis on what role the determination of its properties play in this quest.
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Prof. Manas Kulkarni
International Center for Theoretical Sciences, TIFR, Bangalore
Nonlinear dynamics: From integrable models to cold atomic gases.
9th February, 2018 (Friday)
4:00 pm (Tea at 3.45 pm)
FB382 (A. K. Raychaudhuri Seminar Room)
I will present some fascinating properties in dynamics of integrable models. In particular, I will discuss the Calogero family of models in external potentials. Using certain aspects of integrability, we will discuss duality, solitons and field theory for the Calogero family of models. I will then discuss few integrable and non-integrable models that appear in the context of cold atomic gases and nonlinear optics. I will discuss dynamics, quenches and shock-waves in these models and will present some connection to recent experiments.
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Prof. Chandrabhas Narayana
Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore
Versatility of Raman Spectroscopy in Condense Matter to Biology
1st February, 2018 (Thursday)
5:10 pm (Tea at 5.00 pm)
FB-382 (Physics conference room)
It is going to be 90 years after the discovery of Raman spectroscopy this year. Due to its very low scattering cross sections its development was hampered vis-a-vis absorption techniques, like Infra-red, UV-visible, Fluorescence etc. After the advent of Nano Science and Technology, Raman spectroscopy has found use in every research area. This talk would highlight the recent forays of Raman spectroscopy in the areas hither too not been used. Topological Insulator is one such area. As an example, TiTe2 has been predicted to show a series of pressured induced Topological transitions [1]. Since Topological transitions require a good understanding of the electronic band structure, Angle Resolved Photo Emission Spectroscopy (ARPES) is found to be the ideal direct tool for elucidating these Topological Transitions. Since it is near impossible to do ARPES under pressure, we have used Raman Spectroscopy in combination with x-ray diffraction and resistivity under pressure to demonstrate the existence of multiple Topological transition in TiTe2. In the area of materials chemistry, Metal organic framework (MOFs) has been highly researched topic due to its wide variety of applications, like gas adsorption, catalysis, fluorescence, water splitting etc, due to tailor-able pore sizes simple chemistry. Raman spectroscopy provides an ideal tool to understand the molecular origin of the interactions of guest and host molecules. As an example, we understand the unusual room temperature CO2 uptake in a fluorofunctionalized MOF [2]. In the area of biology, drug discovery and screening for potential drug is a very important area. The golden standard has been Protein Crystallography combined with Docking studies and MD simulations in the quest for potential drugs. We have shown for the first time Raman spectroscopy combined with MD Simulations is a potential drug screening too by understanding the binding cite of a hyper tension drug, Felidipine in cancer therapeutic protein Aurora Kinase [3]. In the present times, Raman spectroscopy provides an ideal tool to study any branch of science. [1] V. Rajaji, Utpal Dutta, et al, Physical Review B (2018) (just accepted paper). [2] Prakash Kanoo, Sandeep Kumar Reddy et al Chemical Communications, 48, 8487 – 8489 (2012). [3] Dhanasekaran Karthigeyan, Soumik Siddhanta et al Proceedings of the National Academy of Sciences (USA), 111, 10416 – 10421 (2014)
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Prof. Anand Kumar Jha
Indian Institute of Technology Kanpur
Efficient measurement of high-dimensional quantum states
25th January, 2018 (Thursday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
High-dimensional quantum information protocols are extremely important as they provide several unique advantages compared to the traditional two-dimensional protocols based on the polarization of photons. This talk will present our recent experimental and theoretical work on developing efficient techniques for measuring the high-dimensional classical and quantum states of light.
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Prof. L. Sriramkumar
Indian Institute of Technology Madras
Can inflation be falsified?
19th January, 2018 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Inflation is presently the most compelling paradigm to describe the origin of perturbations in the early universe. The remarkable success of the inflationary paradigm can be attributed to its simplicity and efficiency. However, the efficacy of the inflationary scenario also seems to be responsible for a major drawback. Despite the strong constraints from Planck on primordial non-Gaussianities, a rather large set of models seems to remain consistent with the cosmological data, even as new models continue to be proposed. I shall begin the talk with an introduction to inflation and the inflationary observables. Thereafter, I shall discuss the performance of a handful of inflationary models against the cosmological data. I shall also touch upon the status of the feasibility of features in the primordial spectrum, an aspect which I have investigated in some detail. I shall then argue that, in the absence of additional theoretical and experimental inputs from beyond cosmology, it may be difficult to falsify otherwise viable models of inflation. In the final stages of the talk, I shall discuss bouncing scenarios as a possible alternative to inflation. With the aid of a specific example (of the so-called matter bounce model), I shall highlight the typical theoretical challenges faced in constructing a convincing alternative.
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Prof. S. Anantha Ramakrishna
Indian Institute of Technology Kanpur
New developments in visualization of latent fingerprints for crime scene investigations
12th January, 2018 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Although the development of DNA identification techniques was initially touted to make other criminal detection methods irrelevant, severe issues of DNA contamination have rendered methods of fingerprint detection and visualization critically important. The detection and visualization of "latent" fingerprints at a crime scene pose inherent challenges with traditional methods like powder dusting failing for majority of surfaces. Recently there has been a surge of developments in fingerprint visualization using different techniques that take advantage of the variety of residues present in fingermarks on varied kinds of surfaces including smooth or rough, porous or non-porous, dry or wet surfaces. These methods take advantage of various physical, chemical as well as optical phenomena. I will review the recent developments in the field and present our recent results [1,2] on latent fingermark visualization on non-porous, rough and reflecting surfaces using vacuum deposition techniques and optical methods. Feedback from experts on various topics is solicited. [1] J. Dutta, S.A. Ramakrishna and I. Mekkaoui Alaoui, Fingerprint visualization enhancement by deposition of columnar thin films and fluorescent dye treatment, Forens. Sci. Int. 228, 32–37 (2013) [2] A.K. Tiwari, S. Guddala, I. Mekkaoui-Alaoui and S. A. Ramakrishna, "Enhanced visualization of latent fingermarks on rough aluminium surfaces using sequential Au and Zn/ ZnS/ ZnO depositions" Journal of Forensic Science, DOI: 10.1111/1556-4029.13686 (online, 2017)
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Prof. Nirmalya Ghosh
Indian Institute of Science Education and Research, Kolkata
Weak measurements on Spin Optical effects
13th November, 2017 (Monday)
5:10 pm (Tea at 5 pm)
FB-382 (Physics conference room)
Spin orbit interaction (SOI) dealing with the coupling of spin (SAM, circular / elliptical polarization) and orbital angular momentum (OAM) of light is under recent intensive investigations because of their fundamental nature and potential applications. The SOI of light has been observed in various optical interactions leading to a number of interesting and intricate spin optical effects, e.g., Spin Hall effect (SHE) of light, spin dependent vortex formation etc. However, these spin optical effects are usually rather tiny and accurate measurement / unique interpretation of these are extremely challenging. Weak measurement, introduced by Aharonov, Albert, and Vaidman is an extraordinary concept that enables faithful amplification and high precision measurement of small physical parameters. Even though it is a quantum mechanical concept, it can be understood using classical electromagnetic theory of light and thus can be naturally extended into classical optics. Indeed, carefully designed experiments were able to verify the validity of the concept in optical systems. In this talk, I shall introduce the concept of optical weak measurements and discuss its applications for the amplification of the tiny spin optical effects of classical light beam. In this regard, I shall highlight a new concept of weak measurement on using the asymmetric spectral response of Fano resonance as a natural pointer generated within the system. The theoretical framework of the concept and its experimental realization in precisely designed metamaterials, namely, waveguided plasmonic crystals will be discussed.
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Prof. V. Ravishankar
Indian Institute of Technology Delhi
The logic route to non classicality of states
6th November, 2017 (Monday)
5:10 pm (Tea at 5 pm)
FB-382 (Physics conference room)
There is an explosion in the number of criteria that are (being) evolved to understand non-classical features of quantum states. I endeavour to show that they acquire a natural formulation in the language of a particular implementation of quantum logic. The talk assumes acquaintance with with basic quantum mechanics, and pretty much just that.
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Prof. Daniel Grumiller
Vienna University of Technology, Austria
Soft Heisenberg hair
30th October, 2017 (Monday)
5:10 pm (Tea at 5 pm)
FB-382 (Physics conference room)
"Soft hair" refers to zero energy excitations of black holes or other entities with horizons. This notion was introduced by Hawking, Perry and Strominger two years ago. From a near horizon perspective it was shown by Afshar and collaborators that soft hair falls into representations of infinite copies of the Heisenberg algebra, with surprising consequences for the entropy of black holes or cosmological spacetimes. I provide an introduction to black holes with soft Heisenberg hair and outline what we hope to learn from this new perspective about their entropy, in particular their microstates.
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Prof. Prabhat Mandal
Saha Institute of Nuclear Physics, Kolkata
Topological insulators and 3D Dirac semimetals: novel electronic materials
23rd October, 2017 (Monday)
5:10 pm (Tea at 5 pm)
FB-382 (Physics conference room)
The electronic properties of graphene, which is a 2D Dirac semimetal, have opened up a new window in condensed matter physics research and device applications. The surface states of several materials such as B1_xSb_x, Bi_Se_3, Sb_2Te_3 and Bi_2Te_3 have striking similarities with graphene. In these materials, known as topological insulators, the bulk has a full insulating energy gap, whereas the surface possesses gapless highly conducting states. As a result, the electrical conduction is dominated by the surface. Following the discovery of topological insulators, another new class of materials, 3D Dirac semimetal, which is 3D analog of graphene has been reported recently. In this seminar, I present some of our recent works on electronic transport properties of topological insulators and 3D Dirac semimetals.
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Prof. Manas Khan
Indian Institute of Technology Kanpur
Decoding Complexity in Working with Complex Fluids
18th October, 2017 (Wednesday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Most of the soft materials that we have around us are multi-component materials exhibiting non- Newtonian rheology. These soft materials are commonly called as complex fluids. The characteristic mechanical properties of complex fluids govern various processes - starting from the preparation of a delicious dish in the kitchen to maintaining the shape of a cell in our body. The origin of these useful mechanical properties is their exotic structural properties. While the complex fluids look homogeneous at macroscopic scale, they are disordered at the ‘microscopic’ scale, and possess structures at an intermediate scale. Due to these intricacies it is not easy to probe the mechanical properties of complex fluids, given by their viscoelastic moduli, reliably. In this talk, with a brief introduction to microrheology, which is the most common experimental technique to probe the viscoelastic moduli of complex fluids, I will discuss different ways to tackle challenges related to working with complex fluids and in complex environments. These include a new microrheology technique that can probe shear-induced anisotropy in complex fluids, along with our modeling and simulations of microrheology in different complex fluids and environments. Our results provide guidelines for accurate microrheology measurements and data analysis that yield reliable system properties.
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Prof. Shyamal K. Bhadra
Indian Association for the Cultivation of Science, Kolkata
A new twist of light by photonic crystals
15th September, 2017 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Light is composed of colours. We see the beauties of the world through delicate combination of these colours. Some of the natural species like peacock and butterfly show sublime landscape of colours through iridescence or structural colouration. Artificially, similar colours can be created or trapped in delicately crafted photonic crystals. With little twist of photonic crystal one can generate helical Bloch mode or helical wavefront. In mid 1980s band gap properties in photonic crystals are demonstrated - resulting multifarious applications in micro-cavities, compact waveguides, optical filters. In later part of development gas-filled photonic bandgap optical fiber and solid core photonic crystal fiber facilitated making of deep UV laser and broadband supercontinuum light sources. Fascinating properties of noble metal-filled hollow core photonic crystal fiber (HCPCF) can be utilized for plasmonic sensors to estimate minute change in refractive indices of flowing analyte like biofluid. In another significant development it has been shown that trapping of Dirac mode in photonic crystal is possible and extending further Dirac mode guidance in specially designed HCPCF is demonstrated. In photonic crystal cladding of HCPCF two photonic bands can create Dirac cones by linearly crossing each other at Dirac point. This typical photonic bands are useful for trapping of light which is otherwise impossible. It has now been shown that helical or topological optical modes can be trapped in twisted HCPCF. Some of the above stated aspects will be discussed.
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Prof. Subhendra Mohanty
Physical Research Laboratory, Ahmedabad
Looking for underground resources with satellite borne atomic clocks
8th September, 2017 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Underground aquifers, oil and mineral deposits change the local gravitational potential in the vicinity. I will describe a proposal to map underground density changes using atomic clocks on satellite which could be used for making maps of underground aquifers and other resources.
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Prof. Parongama Sen
University of Calcutta
Physics of opinion dynamics: theory and reality
5th September, 2017 (Tuesday)
3.30 pm (Tea at 3.15 pm)
FB-382 (Physics conference room)
“Universal” and emergent behaviour existing in many social phenomena have inspired extensive research by physicists in recent years. One of the most extensively studied problems is that of opinion formation in a society. A few models of opinion dynamics which have close resemblance with classical spin systems are to be discussed and some recent results will be reviewed. Two particular problems will be in focus. The first is how an initial minority can influence the entire population. The second one deals with the cases of US presidential elections where the popular candidate getting the maximum individual votes can turn out to be the loser in an electoral college system as it happened in 2016.
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Prof. Umakant Rapol
Indian Institute of Science Education and Research (IISER), Pune
Quantum Networking: The essentials of distributed quantum computing
1st September, 2017 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Quantum Mechanical bits (QUBITS) armed with features of superposition and entanglement offer enormous possibilities in solving some of the most challenging physical problems. The main drawback is the scalability of the no of QUBITS due to the loss of quantum coherence. One of the ways to mitigate this issue is by coupling quantum registers connected by a quantum link, similar to classical networking of multiple computers/processors. In this talk, I will describe some of the systems that are currently being investigated as ‘Nodes’ and the methods that are being developed for reversible mapping of the internal quantum state of QUBITS to a photon and vice-versa. Emphasis will be on experimental methods in mapping Quantum information between individual atoms and photons. In the end, I will present some of the ongoing experiments in our group that are targeted towards addressing the issues of coherence control and quantum coupling.
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Prof. Bhavtosh Bansal
Indian Institute of Science Education and Research (IISER) Kolkata
When first-order phase transitions become zeroth-order and look like second-order transitions
11th August, 2017 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
It is well known that we can easily superheat water to above 100 degrees celsius in a microwave oven and then make it violently boil by a small disturbance that may help bubbles to nucleate. Such first-order phase transitions can also show hysteresis, i.e., the observed boiling temperature may be higher than the condensation temperature. The temperature window of the hysteretic region represents a metastable phase where equilibrium thermodynamics breaks down and we may observe strange glass-like behaviour—-kinetic arrest, ageing, and rate-dependent effects. In this talk I will try to show that the dynamical behavior for a special subset of such hysteretic transitions, where thermal fluctuations are not too important due to long-ranged interactions, may actually be described in very simple terms and mimic some features of second-order phase transitions. In particular, I will discuss the experimental observation of scaling of dynamical hysteresis and phase-ordering after a thermal quench following critical dynamics. I will also briefly discuss some generic characteristics of thermal hysteresis loops and the problems arising from the non-equivalence of ensembles for non-convex free energies. All experiments are performed around the strongly hysteretic Mott transition in vanadium sesquioxide (V2O3), which we have taken as our model system.
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Prof. Satyajit Banerjee
Indian Institute of Technology, Kanpur
Investigating features of equilibrium and non-equilibrium phase transition using vortices in superconductors as a prototype
13th April (Thursday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Vortices in type II superconductors are string like entities carrying with them a fixed quantum of magnetic flux. Often the behaviour of a collection of vortices mimics the behaviour of a collection of interacting classical particles. A collection of vortices exhibit intriguing evolution across different structural phases produced under the influence of thermal fluctuations, disorder and drive. Due to the ease with which the density and interaction between vortices can be tuned, vortices in superconductors act as a convenient prototype for investigating features of equilibrium and non equilibrium phase transition phenomena. To illustrate some of the above issues I will discuss two examples: (i) thermal melting phenomena of a vortex solid and discovery of an unusual low density vortex liquid to solid phase transition, which is not encountered in usual melting of condensed matter solid, (ii) non-equilibrium vortex depinning transitions with specific emphasis on instability driven vortex Jamming phenomenon found in a traffic of moving vortices. I will discuss how such transformations are quantitatively investigated using tools like non-equilibrium fluctuation relations.
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Prof. Aninda Sinha
Indian Institute of Science, Bangalore
Wilson-Fisher without Feynman diagrams
7th April (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Wilson’s renormalization group ideas form a cornerstone of modern quantum physics. They lead to a field theory understanding of critical phenomena. However, the enhanced symmetries at the critical point, namely conformal symmetries are not used as a result of which the calculations, which typically depend on evaluating and regularizing Feynman diagrams, are tedious and complicated. In 1974, Polyakov had put forward an idea based on the consistency between the operator product expansion (OPE) and crossing symmetry, which lay dormant for many years. I will revisit this idea and show how a reformulation in Mellin space leads to enormous calculational advantages—this leads to conformal bootstrap in Mellin space. The building blocks, in their modern incarnation, are what are called Witten diagrams in the AdS/CFT parlance. The calculational steps are manifestly finite. Several standard results (eg. those found in Wilson-Kogut) are easily reproduced and several new results for the OPE coefficients, which are difficult to obtain in the diagrammatic approach, are obtained.
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Prof. Chiranjib Mitra
Indian Institute of Science Education and Research, Kolkata
Experimental quantification of entanglement in low dimensional spin systems
31st March (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Starting from the basic definitions of entanglement measures, we shall report the macroscopic entanglement properties of a low dimensional quantum spin system by investigating its magnetic properties at low temperatures and high magnetic fields. The temperature and magnetic field dependence of entanglement from the susceptibility and magnetization data is performed and comparison is made with corresponding theoretical estimates. Extraction of entanglement has been made possible through the macroscopic witness operator, magnetic susceptibility and heat capacity. The spin systems studied exhibit quantum phase transition (QPT) at low temperatures, when the magnetic field is swept through a critical value. We show explicitly, using tools used in quantum information processing (QIP), that quantum phase transition (QPT) can be captured experimentally using quantum complementary observables. Entanglement properties of the same quantum spin systems when investigated by heat capacity measurements also capture the QPT.
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Prof. Rajdeep Sensarma
Tata Institute of Fundamental Research, Mumbai
Potential Inhomogeneities in Presence of Strong Interactions: Birth and Death of Superconductors
9th March (Thursday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Strong repulsive interactions and potential inhomogeneities both tend to localize Fermions on a lattice and lead to loss of superconductivity. The natural question that comes up is whether they compete or complement each other when both are present in a system at the same time. In this talk, we will use a effective Hamiltonian approach which treats both interactions and inhomogeneities on the same footing to look at two systems: (a) the Ionic Hubbard Model at half-filling, where a staggered potential on a bipartite lattice competes with interactions to delocalize charge and give birth to a novel superconductor. The superconducting Tc scales with the bandwidth of the system and shows a non-monotonic behaviour with the staggered potential, (b) the disordered Hubbard model away from half-filling, where weak disorder competes with strong interaction to preserve superconductivity, but strong disorder complements interactions leading to sudden death of superconductivity in this system.
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Prof. Ambar Jain
Indian Institute of Science Education and Research, Bhopal
Jets in QCD and at Colliders
23rd February, 2016 (Thursday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
I will provide a brief overview of jets in QCD and jets observed at colliders. I will expose the audience to various tools and techniques used to study jet physics and reflect upon the new trends in jet physics. I will also present some new and exciting results for particle tagging, identification and vetos.
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Prof. Goutam Sheet
Indian Institute of Science Education and Research, Mohali
Tip-induced superconductivity in topological materials
17th February, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
It has been recently observed that certain novel phases of matter, like superconductivity, emerge at mesoscopic interfaces between elemental metals and topologically nontrivial systems like topological insulators and topological Dirac and Weyl semimetals. In this talk, I will review some of the published results on such phases with special emphasis on tip-induced superconductivity (TISC). Since the superconducting volume fraction in a TISC is extremely small, traditional bulk characterization tools like regular transport and magnetization measurements fail to detect such a phase. I will highlight how investigation of other hallmarks of superconductivity through point contact spectroscopy becomes useful in detecting such phases. Furthermore, point contact spectroscopy also provides useful information about the nature of superconductivity in a TISC.
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Prof. Diptiman Sen
Indian Institute of Science, Bangalore
Studies of topological insulators: edge states and granular films
9th February, 2016
5.00 pm (Tea at 4.45 pm)
FB 382
In this talk, we discuss two studies of three-dimensional topological insulators like Bi_2 Se_3. As an introduction to topological insulators, we discuss the bulk Hamiltonian of Bi_2 Se_3 near the origin of the three-dimensional Brillouin zone. We show how the Hamiltonians on different surfaces of the system can be derived from the bulk Hamiltonian. The surface Hamiltonians have a massless Dirac form with the spin and momentum of the electron being related in a special way. We then discuss our work on the edge lying between two surfaces of this system. We find that a potential barrier applied along such an edge gives rise to states which are localized along the edge. We use a lattice model to study these edge states in detail. These states have an unusual energy-momentum dispersion. We show that the dispersion can be tuned by varying the barrier strength; in particular the edge states have an almost flat dispersion at a particular value of the barrier strength. Next we discuss experiments indicating that a granular thin film of Bi_2 Se_3 can behave like a single topological insulator crystal. Magnetoconductance measurements show signatures of surface states despite the granularity. However this system has distinctly different properties from conventional bulk TI systems including surface state coupling-decoupling transitions, large surface state penetration depths and Berry phase effects. We present a model which explains these results. Our findings illustrate that granularity can be used to engineer TIs and can allow access to certain features which are difficult to observe in single crystal systems.
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Prof. Tapobrata Sarkar
Indian Institute of Technology Kanpur
Information on Information
2nd February, 2017 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
The geometry of information finds wide applications in areas ranging from simple day to day thermodynamical systems to space-time singularities called black holes. The latter can be related to strongly coupled quantum field theories via the so called gauge-gravity duality. Current progress indicates that one can in principle address all these issues in a unifying framework. In this talk, we will discuss some important recent developments in the subject. We start from information in basic thermodynamics, comment on this in the context of statistical mechanics and field theories, and end with a recent conjecture by Susskind that black holes might be examples of the fastest computers.
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Prof. Arul Lakshminarayan
Indian Institute of Technology Madras
Of quantum chaos, entanglement, and randomness
27th January., 2017 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
We will discuss the basics of entanglement before embarking on its interplay with the spectra of few-body quantized classically chaotic systems and many-body non-integrable spin chains. We will discuss how these can produce psuedo-randomness that can be used for quantum communication protocols, especially encryption and data hiding.
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Prof. Jayanta K. Bhattacharjee
Harish-Chandra Research Institute, Allahabad
OSCILLATORS : OLD AND NEW
24th January, 2017 (Tuesday)
5.00 pm (Tea at 4.45 pm)
L1
Oscillators have played a major role in the developments of various ideas in physics and applied mathematics. A game which started a few centuries ago is still quite alive and leading to insights whose impact can be felt across disciplines. In this talk I will try to focus on some of the aspects ( meaning those which I am competent to discuss! ) beginning with Galileo who started it all and coming down to the renormalization group which puts the dynamics of oscillators at par with other developments of the last few decades.
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Prof. Ayan Banerjee
Indian Institute of Science Education and Research (IISER) Kolkata
Light-bandi?!': demonstrating the 'control' of light over mesoscopic matter using optical tweezers
13th January, 2017 (Friday)
5.00 pm (Tea at 4.45 pm)
FB-382 (Physics conference room)
Optical tweezers confine mesoscopic particles by generating a gradient force of dipolar origin that is restoring in nature and produced by tight focusing of light. Particles can be trivially moved by moving the light beam itself, or by using angular-momentum carrying beams that lead to rotational motion of trapped particles. In this talk, we shall describe two methods where complex motion can be generated in trapped particles without moving the beam or using tailored beams, and thus demonstrate the absolute ‘control’ that light can exercise over mesoscopic matter. In the first method, we utilise effects of the spin-orbit interaction of light generated by the act of tight focusing itself. Thus, there appears a spin-redirection topological phase in the beam, as well as a longitudinal component in the electric field that produces transverse energy flows leading to the transverse separation of the two constituent opposite circular polarization modes of the input linearly polarized state (spin-Hall shift). We accentuate these effects by using a stratified medium in the path of the trapping beam so that the intensity distribution near the focal plane contains polarization dependent side lobes where particles are preferentially trapped and can be moved by simply changing the polarization state of the input beam. Also, regions of opposite circular polarization are produced in the vicinity of the focus, where particles spin in a controllable manner. In the second method of generating dynamics in particles, we create microbubbles in an aqueous suspension of a material (soft oxometalate or SOM) absorbing at the trapping laser wavelength. The temperature gradient across a single microbubble causes a surface tension gradient that generates Marangoni flows in the water around the bubble. Mesoscopic particles are dragged by the flow and self-assemble to form patterns along the sample chamber wall where the bubble is localised. In addition, local flow vortices – indirectly controlled by light – are created, resulting in rotational motion of particles akin to that produced by angular momentum carrying beams.
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Prof. Anandamohan Ghosh
Indian Institute of Science Education and Research (IISER) Kolkata
Statistics of Lyapunov Spectrum for Randomly Coupled Systems
6th January, 2017 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
The sensitivity of spatiotemporal dynamics to small changes in initial conditions can be quantified by computing the Lyapunov spectrum. The collective dynamics of coupled units arranged on a random network in the limit of weak coupling is chaotic with all Lyapunov exponents positive. On the other hand, in the case of strong coupling synchronization is observed, with the largest Lyapunov exponent positive and the rest of the spectrum is negative. In this lecture, simple tools of Random Matrix Theory will be reviewed and applied to the Lyapunov spectrum of randomly coupled systems. The statistics of gaps in the Lyapunov spectrum show universal Poisson and Wigner like distributions corresponding to the chaotic and the synchronized phases, respectively. Interesting dynamical phases are observed for intermediate coupling strengths and a possible explanation using random matrix theory of asymmetric matrices will be discussed.
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Professor Bikas K. Chakrabarti
Saha Institute of Nuclear Physics, Kolkata
Econophysics of Income and Wealth Inequalities
3rd November, 2016 (Thursday)
5.00 pm (Tea at 4.45 pm)
FB-382 (Physics conference room)
Inequalities in income and wealth distributions have been a permanent feature of the societies in any civilization, and are characterized by established and universal laws. The century old kinetic theory for the gases had long been identified as a possible tool to explore the origin of such inequalities. Such kinetic exchange formulations for social dynamics will be discussed and the recent developments will be indicated. Extensions of the kinetic theory to collective opinion formations in societies will also be discussed.
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Prof. Sreerup Raychaudhuri
Tata Institute of Fundamental Research, Mumbai
Electroweak Physics - The Catastrophe of Success
28th October, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
The Standard Model of electroweak physics has proved to be one of the most successful models ever developed to describe the natural world. In this talk, some of these successes will be described briefly. It will then be discussed how the model itself is a patchwork of different ideas, held together with experimentally-fitted parameters, and should, by rights, be replaced by a more fundamental theory. Attempts at building such theories will be described and it will be shown how the runaway success of the Standard Model is now standing in the way of further progress - leaving us, for the present, in a predicament rather like the one described by Tennessee Williams in his poignant 1947 essay. Finally, some speculations about the possible future will be presented, in brief.
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Prof. S. Rangwala
Raman Research Institute, Bangalore
Interactions in a trapped ion-atom system
6th October, 2016 (Thursday)
5.00 pm (Tea at 4.45 pm)
FB-382 (Physics conference room)
Cooling and trapping of atoms and ions has resulted in path breaking advances ranging from metrology to condensed matter physics and beyond. A significant and exciting leap towards new possibilities in ultracold physics is the co-trapping of ions and atoms in hybrid traps. This opens up several new classes of interactions for precision experiments. In this talk, I shall discuss some of the interesting and motivating ideas behind the experiments in this direction, discuss briefly the motivations behind the experiments at RRI in this direction, and present some important results from RRI that contribute to efforts in this direction. I shall also summarize some selected key results from other groups in the area, which underlines the course of major future directions in the field, with particular reference to statistical and condensed matter physics. This is still possible with cooled and trapped ion-atom systems as the number of contributions in this now rapidly growing area is still modest compared to more matured fields, and therein lies the excitement.
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Prof. S. Ramakrishnan
Tata Institute of Fundamental Research, Mumbai
Superconductivity at extremely low carrier density: Bismuth
30th September, 2016 (Friday)
5.00 pm (Tea at 4.45 pm)
FB-382 (Physics conference room)
Bismuth(Bi) has played a very important role in uncovering many interesting physical properties in condensed matter research and continues to draw enormous scientific interests due to its anomalous electronic properties. Unlike metals where there is roughly one mobile electron per atom, in a semi-metal like Bi, the concentration of mobile electrons is extremely low (100,000 atoms share a single mobile electron). Hence, the superconductivity (SC) in bulk Bi is thought to be very unlikely at a currently achievable temperature (~40 μK). In this talk, I will describe the first-ever observation of bulk SC in Bi single crystals (99.9999%) below 530 μK under ambient pressure with an estimated critical magnetic field of 5.2 μT (one fifth of earth’s magnetic field) at absolute zero. The standard models (superconductivity) cannot explain this phenomenon because the characteristic thermal energy is comparable to the Fermi energy in Bi and a new theory is necessary.
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Prof. Gautam Mandal
Tata Institute of Fundamental Research, Mumbai
Black holes, entanglement and thermodynamics
23rd September, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Dynamics of a closed system is deterministic and time reversal invariant. How does a thermodynamic description of such a system emerge? A partial answer comes from a study of quantum entanglement between parts of a closed system. Another intriguing hint comes from gravitational collapse into a black hole using the concept of gauge/gravity duality. In this colloquium I will review some of these developments, both theoretical and experimental, and present some recent results.
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Prof. P. S. Anil Kumar
Indian Institute of Science, Bangalore
Current induced magnetization reversal in perpendicularly magnetized systems
9th September, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Spintronics or magneto-electronics is an area of active research because of the tremendous potential both in terms of fundamental physics and technology. Here, one exploits the spin degree of freedom of the electrons along with its charge. So, spintronics combines standard microelectronics with spin-dependent effects. Hence, one can expect a new generation of devices with completely different functionality. The advantages of these magnetic devices would be non-volatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared to semiconductor devices. This has led to a revolution in magnetic data storage technology. Present day data storage heavily relies on magnetic hard disc drives in the form of magnetic thin film media and one of the key concerns is the magnetization reversal of the magnetic data bits by applying local magnetic fields. The replacement of magnetic field assisted reversal by more sophisticated spin transfer torque mechanism is emerging as a viable and attractive option for next generation technology. This mechanism requires source of spin polarized electrons from a ferromagnet to switch the magnetization of soft ferromagnet in spin valves or magnetic tunnel junctions. Recently, a different route of generating spin polarized current using heavy metals like Pt by utilizing the phenomenon of Spin Hall Effect is catching tremendous attention. Here, a charge current is converted into a spin current in the spin Hall metals which is injected into an ultrathin ferromagnetic layer to induce magnetization reversal by spin transfer torque. Normally this torque requires assistance of magnetic field to attain deterministic switching of magnetization, but as a case study we show that by utilizing in-plane asymmetry of the ultrathin ferromagnetic films we can attain deterministic switching of magnetization without any field assistance. This involved careful optimization of anisotropy of the Pt/Co/Pt thin films with Co thickness down to 0.35nm and the understanding of interfaces. In this colloquium, I will be giving an overview of magnetic memory concepts, magnetic domain wall engineering, current induced magnetization reversal etc. with case studies.
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Prof. Mustansir Barma
TIFR Centre for Interdisciplinary Sciences, Hyderabad
Fluctuations and Order
6th September, 2016 (Tuesday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
It is common wisdom that very large random fluctuations would succeed in destroying an ordered state. While this statement is almost always true, there are interesting exceptions; these exceptionally interesting systems are the focus of this talk. Giant fluctuations coexisting with long range order are seen in models of passive scalars, active biological systems and granular media, and experiments on vibrated rods. These will be discussed, along with the unusual signatures that characterize fluctuation-dominated order.
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Professor Arnab Sen
Indian Association for Cultivation of Science, Kolkata
Disorder as a probe for spin liquids
2nd September, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Spin liquids, despite their apparently featureless ground states, are rather exotic magnetic states which host fractionalised excitations and emergent gauge fields, unlike ferromagnets or antiferromagnets. Interestingly, quenched disorder can nucleate defects with unusual properties and thus reveal the hidden collective excitations of such states. In this talk, having introduced the basics, I will discuss how disorder can act as a powerful probe for the diagnosis of spin liquids.
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Prof. K. Thyagarajan
Department of Physics, IIT Delhi
Integrated optic devices for the generation and manipulation of entangled photon pairs
26th August, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Quantum properties of light are being exploited for various applications in the field of information and communication technologies. Spontaneous parametric down conversion (SPDC) involving the second order nonlinear optical effect in which a pump photon splits into a pair of photons is one of the most important process used for the generation of entangled photon pairs and is expected to find applications in a wide variety of quantum optics based systems. Increased complexity of quantum devices for generation and manipulation of photons can be realized by using the well developed integrated optic technology leading to integrated quantum photonic circuits. Such circuits also provide the designer with optimum devices with higher efficiencies and new geometries. The talk will discuss the process of SPDC in optical waveguides and present our recent work in the design of integrated optic waveguide devices for the generation and manipulation of polarization and mode entangled photon pairs.
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Prof. Sagar Chakraborty
Department of Physics, IIT Kanpur
Synchronizing by uncoupling!
19th August, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
I shall present a scheme for synchronizing chaotic dynamical systems by transiently uncoupling them. Specifically, systems coupled only in a fraction of their phase spaces may synchronize even if, when fully coupled, they do not do so. For many standard systems coupling strengths need to be bounded to effect synchrony. Transient uncoupling removes this bound and enables synchronization in an infinite range of effective coupling strengths. Additionally, the transient coupling scheme opens up the possibility to induce synchrony in (biological or technical) systems whose parameters are fixed and cannot be modified continuously. One can also extend the scheme to induce generalized synchronization in both unidirectionally and bidirectionally coupled populations of chaotic systems. Further, we demonstrate that transient uncoupling scheme is capable of counteracting the usual disruptive effect of noise on synchronization.
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Prof Subroto Mukherjee
FCIPT Division, Institute for Plasma Research, Gandhinagar, Gujarat
Environment Friendly Plasma Technologies: Developments at Institute for Plasma Research
5th August, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
L6 (Lecture Hall Complex)
Plasma, the 4th state of matter after solid, liquid and gas comprises of matter in an excited state. Matter in plasma state starts conducting electricity, comprises of ions, electrons, radicals, complex molecules, uv-visible radiation and one can perform various modifications on the material surface that it interacts with. For environment friendly applications of plasmas one can use either the extreme heat content of atmospheric pressure plasma or use the reactive species present in low pressure plasma. Plasma pyrolysis is a process that uses the high heat content of atmospheric pressure plasmas to dissociate complex long-chain molecules of polymer (present in biomedical, industrial and plastic waste) and form harmless inflammable gases like methane, ethane, carbon monoxide and either use them as fuel or burn them. When plasma pyrolysis is used with energy recovery concept, it is generally energy efficient process provided the waste has a calorific value. Recent developments are in the field of waste flower disposal in the vicinity of religious sites and disposal of caracass, and plasma pyrolysis disposes them in a complete environment friendly manner. Subatmospheric pressure plasma is very good in generating active species which can be used for above surface or subsurface modification. On above surface modification, plasma etching as well as deposition of compounds can be done using plasmas. When the plasma comprises of nitrogen, it can be implanted and diffused inside steel components to increase the lifetime of industrial components. Emerging applications of plasmas are in the field of skin-disease treatment, modification in germination rate of seeds, killing of bacteria in food and sterilization of biomedical equipments, pesticide removal and various other applications, all done in an environment friendly manner. At FCIPT Division of Institute for Plasma Research, R&D on all the areas are being pursued in developing plasma based technologies that are environment friendly and benefits the society.
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Professor Soumitra Sengupta
Indian Association for Cultivation of Science, Kolkata
Miracles of extra dimensions
29th July, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
L6 (Lecture Hall Complex)
Our observable universe has three space and one time dimension. To describe this universe, most of the theoretical models are therefore formulated in a four dimensional space-time with some underlying symmetries. Such theories, despite many successes, have limitations which are yet to be resolved. Can the presence of additional spatial dimension resolve these issues ? If such extra dimensions exist, why have we not been able to see them yet? What could be the possible signatures of their invisible presence and how can they influence the Physical laws as well as phenomenological outcome of our observable universe ? In this talk I shall try to address how the evolution of this idea over the years points towards some remarkable influences of extra dimensions on our visible universe.
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Professor Pavan Kumar
Indian Institute of Science Education and Research, Pune
Nanophotonics based on Exciton-Polaritons
8th April, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Collective excitations in solids, such as plasmon-polaritons and exciton-polaritons, have emerged as versatile platforms to control light at nano-scale. In this talk, I shall introduce some basic aspects of exciton-polaritons, their variety and utility as nanophotonic platforms. Specifically, I shall discuss about nanophotonic response of certain organic molecular meso-architectures that support Frenkel exciton-polaritons.
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Professor Anand Kumar Jha
Department of Physics, IIT Kanpur
Transfer of quantum correlations from one-photon systems to entangled two-photon systems.
1st April, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
The simultaneous existence of both particle and wave properties is the most distinguishing feature of quantum systems. Just as particle-like properties are characterized by physical observables such as energy, momentum, angular-momentum, etc., the wave-like properties are characterized by correlations, the degree of which can be quantified in terms of the contrast with which a system produces interference patterns. This talk will consider processes in which one-photon systems break up to produce systems of two entangled photons and will discuss how the particle and wave properties get transferred in such processes. It is well established that in such processes, the particle-like properties get transferred in a conserved manner. For example, the sum of the energies of two entangled photons remain equal to the energy of the original photon. However, it is not very well understood as to how the wave-like properties, that is, the correlations, get transferred from one-photon to two-photon systems? This question is intimately connected to another very important question as to how the entanglement of two-photon systems get affected by the correlations of the original one-photon systems. A definite answer to these questions not only is essential for a deeper understanding of entanglement but also will have important implications for entanglement-based applications. This talk will go through the basics of correlations and two-particle entanglement and will present our recent results that attempt to answer some of the above questions.
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Professor Sourin Das
University of Delhi
Non-local multi-particle geometric phases in electronic intensity interferometry
18th March, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Berry's discovery of the geometric phase in 1984 led to a deeper understanding of wide range of phenomena in different areas of physics starting from molecular physics to condensed matter systems. In this talk, I will first provide an introduction to the concept of geometric phase in spirit of Berry's definition and then relate it to its generalized version as anticipated in earlier works of Pancharatnam. I shall then apply Pancharatnam's ideas to obtain non-local and multi-particle geometric phase in the context of electronic version of the Hanbury-Brown and Twiss intensity interferometer. I will discuss a possible experimental realization of this effect by exploiting edge states of two-dimensional topological insulators (2d TI). It will be shown that the electrical transport in quantum spin Hall (an example of the 2d TI state) edge can host a two particle Aharonov - Bohm (AB) effect in spin space which essentially is an example of multi-particle and non-local geometric phase. This two particle “spin A-B effect” stems from an effective AB flux piercing a two particle loop identified on the Bloch sphere which can be attributed to an abstract monopole of strength 1/2 placed at the origin of the sphere.
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Professor Prateek Sharma
Indian Institute of Science, Bangalore
Black Holes in Our Universe
10th March, 2016 (Thursday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Observations show that astrophysical black holes (BHs) occur in two classes: stellar mass black holes, the end results of the death of massive stars; and supermassive black holes (SMBHs), occurring at the centers of most galaxies.The SMBHs play a crucial role in regulating cooling of gas (and hence star-formation) in dark matter halos. I will present numerical simulations of energetic jets driven by SMBHs and their interaction with the hot gas in halos (best observed in galaxy clusters), the ultimate raw material for forming stars in galaxies. These simulations produce morphologies similar to observations and can suppress star formation to a value inferred from observations. Very recently gravitational wave detectors detected a merger of ~30 solar mass BHs. These are the most massive stellar mass black holes that we know. I will briefly discuss the implications of this discovery on BH demographics.
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Prof. Lokesh C. Tribedi
Tata Institute of Fundamental Research (TIFR), Mumbai
Recent trends in atomic collision studies in bio-molecules, PAHs and fullerenes
4th March (Friday), 2016
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Present-day atomic collision physics is closely related to interdisciplinary science. Collisional interactions of fast ions or electrons with clusters and other mesoscopic objectsare useful to bridge the gap between gas atoms and bulk solids. A homo-nuclear diatomic molecules, such as, H2 can even be considered as a smallest double-slit to observe Young type electron interference. The complex allotropes of carbon, such as, fullerenes, nanotubes, large organic molecules of biological (DNA bases) interest and PAH molecules have been at the focus of recent atomic collision research. The secondary electron emission from nucleobases and water is an important parameter to estimate the radiation damage caused by fast ions. Atomic processes are influenced when the fast ion passes through a mesoscopic object due to collective plasmon excitation. The C60 fullerene is used as a bench mark system which manifests the giant plasmon resonance. A similar plasmon excitation in the PAH molecules has been demonstrated only recently which will have implications in astrochemistry and plasmon devices. A recently installed ECR based -ion-accelerator in TIFR and the existing 14 MV Pelletron tandem accelerator are used along with the electron, recoil-ion and high resolution x-ray spectrometers are used for such experiments.
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Professor Raja Paul
Indian Association for Cultivation of Science, Kolkata
Segregating chromosomes during mitosis: time and error
26th February, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Mitotic spindle is the microtubule based biomechanical machinery that segregates chromosomes to two daughter cells. Evolution of spindle during mitosis relies on the stochastic capture of microtubules at kinetochores in which dynamically unstable microtubules search in space until all the kinetochores are captured. Kinetochore texture is a crucial factor of the efficiency and fidelity of this process with large kinetochores expected to speed up assembly at the cost of accuracy, and smaller kinetochores to suppress errors at the expense of efficiency. We show that at the onset of mitosis kinetochores form large crescent structures that subsequently condense into discrete objects on opposite sides of the centromere. This condensation occurs only after the formation of end-on microtubule attachments. In silico modelling of kinetochore expansion-compaction in the context of lateral interactions correctly predict experimentally-observed spindle assembly times with reasonable error rates. The computational model suggests that larger kinetochores reduce both errors and assembly times, explaining the robustness of spindle morphogenesis and the functional significance of augmented kinetochores..
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Professor Romesh Kaul
The Institute of Mathematical Sciences, Chennai
High Energy Physics: A Reductionist Perspective of Constituents of Matter
19th February, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Quest for the ultimate constituents of matter has a long history. Starting from the earliest times, a survey of various developments leading to present understanding of the elementary particles and the fundamental forces experienced by them will be presented. General theoretical dogmas that govern these developments will be discussed. Role of Large Hadron Collider (LHC) at Geneva in this saga will be outlined with the aim of highlighting present concerns. Expectations of new directions beyond the present day Standard Model (SM) of particle physics will be pointed out.
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Prof. Satishchandra Ogale
Department of Physics and Centre for Energy Science, IISER, Pune.
Seeking Clean Energy Solutions Through Materials Innovation
12th February, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
Our ability to harvest energy efficiently from clean and green sources, and store it effectively for subsequent use in large scale stationary or small scale mobile application sectors will define our future in terms of sustainability and quality of life. Towards this end, new and novel solutions based on advanced functional materials are being intensely sought at the present time. Most such solutions must necessarily ride upon the promise of materials innovation involving a variety of materials systems, and their compositions, morphologies and architectures. In this talk, after a brief introduction to the current scenario, I will discuss some interesting possibilities in this respect by deriving several examples based on the research done in my group in the areas of sensitized cells, photoelectrochemical water splitting and energy storage devices using metal oxide and sulphide nanomaterials, and different functional forms of carbon. I will also address the issues of scalability and cost-effectiveness, which can impact the real-world applicability of laboratory methods and processes.
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Professor Krishnendu Sengupta
Indian Association for Cultivation of Science, Kolkata
Dirac fermions and Majorana bound states in condensed matter systems.
22nd January, 2016 (Friday)
4.00 pm (Tea at 3.45 pm)
FB-382 (Physics conference room)
In recent years, extensive theoretical and experimental research has been carried out on realizations of Dirac fermions and Majorana bound states on condensed matter system. In this talk, I shall provide a brief and pedagogical introduction to some of such condensed matter systems. This will be followed by a brief discussion of transport properties and issues regarding experimental detection of such particles.
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Professor Y N Mohapatra
Department of Physics and Materials Science Programme,
Indian Institute of Technology Kanpur
Cooking with quantum dots: Physics of Recipes for Flexible Electronics
14th January, 2016 (Thursday)
4 pm
FB-382
A new electronic revolution is brewing based on devices which can be fabricated on thin glass, paper, plastic, and cloth. Away from the conventional electronics in a box and a plug, the brave new world of applications need be bendable, flexible, disposable, and of large area making every object smart and intelligent in the new global project of Internet of Things (IoT). The development of such technology relies on one’s ability to print different functionalities such as conductors, semiconductors and dielectrics on flexible substrates almost at will.
In this talk, I will focus on some key physics problems that one faces in trying to realize electronic functionalities based on solution processing and printing. A promising strategy of developing materials for such applications has been to embed quantum dots or similar nanostructures in a disordered polymeric host. The physics of charge processes in these hybrid materials is challenging both from fundamental and technological perspectives. I will illustrate several such issues in the development of bulk heterostructures, where subtle interplay of order and disorder plays a crucial role in determining electronic and optoelectronic properties.
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Professor Amalendu Chandra
Department of Chemistry, Indian Institute of Technology Kanpur
Hybrid Quantum-Classical Studies of an Enzymatic Reaction in Aqueous Solution
1st January, 2016
2.30 pm
FB-382
Transaminase is an enzyme which reversibly catalyzes the transamination reaction. Aspartate Transaminase (AspTase) is a key enzyme of amino acid metabolism process. In the present talk, we will discuss our recent studies on the mechanism of the transamination reaction in the active site of AspTase using hybrid quantum-classical molecular dynamics simulation with the aid of metadynamics technique.
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Professor Abhijit Mookerjee
S.N. Bose National Center for Basic Sciences, Kolkata
DEALING WITH DISORDER
6th November, 2015 (Friday).
4 pm
FB-382
In the world of real materials disorder is ubiquitous.Nevertheless, condensed matter theoreticians still find it difficult to
ditch the Bloch bandwagon : periodicity, plane waves, crystallinity - the lot. We shall declare with Heine "Let us throw k-space out of the window"(Lectures in Physics, vol 35, Academic Press) and face the consequences.The lecture will focus on th
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Professor Sukanta Bose
The Inter-University Centre for Astronomy and Astrophysics, Pune, India
Gravitational waves and the neutron star equation of state
29th October, 2015 (Thursday)
4 pm
FB-382
The two detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) began observation runs a few weeks ago. A few other detectors in the world, possibly including one in India, called LIGO-India, are expected to join them in the coming years to usher in the era of gravitational wave (GW) astronomy. Such a multi-baseline network will be able to localize GW transients, e.g., the merger of neutron star binaries, that it detects to within a few to tens of square-degrees. This presents both an opportunity and a challenge to other observatories that are in pursuit of their electromagnetic (EM) and particle counterparts, e.g., in the form of afterglows. The opportunity is to develop a more complete understanding of these sources. To wit, are short duration gamma-ray bursts and kilonovae indeed associated with the merger of binaries involving neutron stars? On the other hand, the challenge is to be able to scan the large error boxes in the sky of GW networks in an ingenious way so as not to miss observing an EM counterpart. After describing the general aspects of what is clearly a multi-messenger endeavor, I will discuss how Indian telescopes can contribute to this effort. I will also discuss how GW observations of neutron stars can improve our understanding of nuclear interactions in ways that complement the knowledge acquired from terrestrial labs.
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Professor Amit Agarwal
Indian Institute of Technology, Kanpur
Collective spin and density excitations (plasmons) in 2 dimensional electron gas, and Dirac systems (such a graphene)
16th October, 2015 (Friday)
4 pm
FB-382
In this talk we will discuss some of our recent works related to collective spin and density excitations, beginning with our prediction of a new long lived collective spin mode in a two dimensional electron gas. This new spin mode arises as a consequence of the interplay between spin polarization and electron electron interactions, and can be used as a interconnect between spin-torque oscillators. Further we study charge-plasmons in spin polarized graphene, and propose a new way to measure spin polarization. We derive explicit expressions for the plasmon dispersion in the undamped regime. From this, we are able to calculate the critical wave vector beyond which the plasmon enters the electron-hole continuum, its quality factor decreasing sharply. We find that the value of the critical wave vector is strongly spin polarization-dependent, in a way that has no analogue in ordinary two-dimensional electron gases. We show that the effect is robust with respect to the inclusion of disorder and we suggest that it can be exploited to experimentally determine the spin polarization of graphene. Additionally we will also discuss the collective density oscillations of a collection of charged massive Dirac particles, in one, two and three dimensions and their one dimensional superlattice. Our analytical results will be useful for exploring the use of massive Dirac materials as electrostatically tunable plasmonic metamaterials and can be experimentally verified by infrared spectroscopy as in the case of graphene.
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Professor Srubabati Goswami
Physical Research Laboratory, Ahmedabad
Neutrinos: The Invisible Messengers
9th October, 2015
4 pm
FB-382
Neutrinos are all pervading yet elusive. Since its discovery the question which has puzzled physicists is whether they have mass or not. Finally, the observation of neutrino oscillations in terrestrial experiments established that the neutrinos indeed have small but non-zero mass. In this talk I will discuss the salient features of neutrino oscillations, the current status of the oscillation parameters and the present unknowns. I will mention some of the future experiments that can determine these unknown parameters giving special emphasis on the India-based Neutrino Observatory (INO) experiment. I will also discuss some of the implications of small neutrino masses in terms of probing physics beyond the Standard Model.
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Professor Arvind Ayyer
Indian Institute of Science, Bangalore
Two Species Semipermeable Exclusion Processes
11th September, 2015
4 pm
FB-382
One of the primary motivations of nonequilibrium statistical physics is the study of systems connected to reservoirs at different temperatures. In that context, exact solutions of model systems lend insight into the behaviour of real systems. In joint works with E. R. Speer and J. L. Lebowitz, we study and solve exactly one particular model system. We consider two-species variants of the totally asymmetric simple exclusion process (TASEP) on an interval connected to reservoirs. Most of the time will be spent discussing an "integrable" variant in which second-class particles are not allowed to leave. In this case, we can both prove and understand the nonequilibrium steady state and phase diagram in great detail. Time permitting, we will consider other variants which permit exact analysis.
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Professor Pankaj Jain
Department of Physics, Indian Institute of Technology Kanpur
Large Scale Anisotropy in the Universe
4th September, 2015
4 pm
FB-382
The cosmological principle states that the Universe is homogeneous and isotropic on large distance scales. However I will argue that the Big Bang paradigm is consistent with small deviations from this principle. At very early times the Universe need not be isotropic and homogeneous. It acquires this property during the inflationary phase of its expansion. The early anisotropic and inhomogeneous phase can affect observations today, leading to a violation of the cosmological principle. These may provide an explanation for a diverse set of observations that indicate a deviation from the standard expectations of the Big Bang model. These include anisotropy in radio polarization, radio flux, optical polarizations, CMBR large scale anisotropies as well as the hemispherical anisotropy in CMBR. Curiously many of these observation indicate a preferred direction pointing roughly in the direction of the Virgo cluster. I will review these observations and the theoretical models which aim to explain them.
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Professor Dibyendu Das
Indian Institute of technology Bombay
Can spatial order and disorder coexist? Case studies of Porod law violation in non-equilibrium systems.
28th August, 2015
4 pm
FB-382
Although seemingly strange, in many non-equilibrium systems large scale spatial ordering may often coexist with large scale fluctuations. Thus they are neither cleanly ordered nor disordered in the conventional sense. This is in contrast to coarsening systems approaching equilibrium steady states, which usually exhibit growth of clean order, marked by a universal characteristic form of the scaled structure function called the Porod law. In the talk, many systems exhibiting Porod law violation would be discussed. The connection of this violation to the underlying fractal-like spatial density structure would be sketched.
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Professor Avinash Khare
Department of Physics and Astrophysics, University of Delhi, Delhi
A model for the dust cluster explosion
21st August, 2015
4 pm
FB-382
A model for the dust cluster explosion where micron/sub-micron sized particles are accelerated at the expense of plasma thermal energy, in the afterglow phase of a complex plasma discharge is proposed. The model is tested by MD simulations of dust particles in a confining potential. The nature of the explosion (caused by switching off the discharge) and the concomitant dust acceleration is found to depend critically on the pressure of the back ground neutral gas. At low gas pressure, the explosion is due to unshielded Coulomb repulsion between dust particles and yields maximum acceleration while in the high pressure regime it is due to shielded Yukawa repulsion and yields much feebler acceleration. These results are in agreement with recent experimental findings.
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Professor Pratap Raychaudhuri
Tata Institute of Fundamental Research, Mumbai
Real space investigations of the order-disorder transition of the vortex lattice using scanning tunneling spectroscopy
14th August, 2015
4 pm
FB-382
In an ideal Type II superconductor the magnetic flux which enters in the form of quantized flux tubes get arranged in a period fashion through mutual interactions, thereby mimicking a soft periodic solid. However, in real superconductors the perfect periodic order of the flux line lattice is interrupted by structural defects in the crystal, which provide an additional disordered background potential for the flux tubes. The flux line lattice in a Type II superconductor thus provides a versatile model system to study the interplay between interactions and random pinning. In this talk, I will describe our recent investigations on the order-disorder transition of the flux line lattice, using direct imaging through low temperature scanning tunneling spectroscopy. Through simultaneous imaging of the flux line lattice and the crystal lattice, I will show that the order-disorder transition is strongly influenced their mutual coupling which reinforces the orientational order of the flux line lattice. In addition, I will show the existence of several metastable states, which can be accessed through different magneto-thermal cycling.
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Professor Mahendra K. Verma
Indian Institute of Technology Kanpur
Dynamics vs Thermodynamics: Who is the winner?
7th August, 2015
4 pm
FB-382
and Thermodynamics are two pillars of physics; both are used to describe the nature. In this talk, we will contrast the assumptions of these two fields, specially for phase transitions. We will show how bifurcation theory with a small number of variables can describe the hysteresis and phase coexistence suitably. Dynamics provides insights into how initial condition could play a major role in the system’s final state.
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Professor Biswarup Mukhopadhyay
Harish Chandra Research Institute, Allahabad, India
The Messiah of Mass and Message about More
31 July 2015 (Friday)
4 pm
FB-382
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Brajesh Kumar Mani
University of South Florida (USF), Tampa, USA
Many-body methods and physics of atomic and many-atomic system
17 April 2015 (Friday)
4 pm
FB-382
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Gagan Kumar
IIT Guwahati
Terahertz Photonics
10 April 2015 (Friday)
4 pm
FB-382
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Dr. R. Prabhu
HRI, Allahabad
Quantum communication networks
7th April, 2015 (Tuesday)
12 noon
FB-382
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Manoj K. Harbola
Department of Physics, IIT Kanpur
Excited-state energy functionals and ionization potential theorem
27 March 2015 (Friday)
4 pm
FB-382
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Prof. J. S. Yadav
Large Area X-ray Proportional Counter (LAXPC) instrument onboard
ASTROSAT
26 March, 2015 (Thursday)
4 pm
FB-382
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P. Viswanath
Centre for Nano and Soft Matter Sciences, Bangalore
Dynamics of liquid crystalline drops at air-water interface
20 March 2015 (Friday)
4.00 pm
FB-382
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Justin David
Indian Institute of Science, Bangalore
Entanglement entropy and Holography
13 March 2015 (Friday)
4.00 pm
FB-382
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Sunil K. Gupta
TIFR, Mumbai & GRAPES-3 Experiment, Cosmic Ray Laboratory, Ooty
Precision measurements in Astroparticle Physics using state- of-the-art technology in GRAPES-3 experiment
09 March 2015 (Monday)
4.00 pm
FB-382
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Gautam Sengupta
Department of Physics, IIT Kanpur
Space time Holography, Black Holes and Superconductors
27 Feb. 2015 (Friday)
4.00 pm
FB-382
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Shashikant Dugad
Tata Institute of Fundamental Research, Mumbai
Searches for Fundamental Particles: An experimental overview
13 Feb. 2015 (Friday)
4.00 pm
FB-382
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Joydeep Chakrabortty
Department of Physics, Indian Institute of Technology Kanpur
Looking at Particles through a Giant's eye.
10 Feb. 2015 (Tuesday)
4.00 pm
FB-382
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Arvind
Indian Institute of Science Education and Research, Mohali
Quantum entanglement: A central theme in quantum information processing
06 Feb. 2015 (Friday)
4.00 pm
FB-382
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Ujjwal Sen
Harishchandra Research Institute, Allahabad
Strong Subadditivity in Quantum Information
30 Jan. 2015 (Friday)
4.00 pm
FB-382
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Srihari Keshavamurthy
Department of Chemistry, Indian Institute of Technology Kanpur
Eigenstate Thermalization Hypothesis and Intramolecular
Vibrational Energy Flow - connecting two different "worlds"
23 Jan. 2015 (Friday)
4.00 pm
FB-382
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Sankalpa Ghosh
Indian Institute of Technology Delhi
Ultracold atoms in Synthetic Gauge field in an optical cavity
16 Jan. 2015 (Monday)
4.00 pm
FB-382
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Avinash Deshpande
Raman Research Institute, Bangalore
Fascinating Life-stories of Pulsars
09 Jan. 2015 (Monday)
4.00 pm
FB-382
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Gautam I Menon
Institute of Mathematical Sciences, Chennai
The Nuclear Physics of Chromosome Positioning
14 Nov. 2014 (Friday)
4.00 pm
FB-382
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Abhishek Chaudhuri
Indian Institute of Science Education and Research, Mohali
Forced desorption of an active polymer
07 Nov. 2014 (Friday)
4.00 pm
FB-382
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Punyabrata Pradhan
S. N. Bose National Centre for Basic Sciences, Kolkata
Additivity Principle and Mass Fluctuation in Conserved-Mass
Transport Processes
31 Oct. 2014 (Friday)
4.00 pm
FB-382
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B. V. R. Tata
Indira Gandhi Centre for Atomic Research, Kalpakkam
Photonic Crystalline Arrays of Charged and Soft Colloidal Spheres
17 Oct. 2014 (Friday)
4.00 pm
FB-382
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Soumitra SenGupta
Indian Association for the Cultivation of Science, Kolkata
Unveiling space-time mysteries -- an unending quest
10 Oct. 2014 (Friday)
4.00 pm
FB-382
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Jai Sukhatme
Indian Institute of Science, Bangalore
Water Vapour in the Atmosphere - The Advection-Condensation Model
26 Sept. 2014 (Friday)
4.00 pm
FB 382
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Krishnacharya Khare
IIT Kanpur
Limitless Beauty of Soft Matter: Surface and Interfacial Phenomenon (wetting, adhesion, friction and SLIPs)
12 Sept. 2014 (Friday)
4 pm
FB-382
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Subrata Pradhan
Institute for Plasma Research, Gandhinagar
SST-1: The First Indian Superconducting Tokamak
05 Sept. 2014 (Friday)
4 pm
FB-382
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Joydeep Chakrabortty
IIT Kanpur
Looking at Particles through a Giant's eye
4 pm
29 Aug. 2014 (Friday)
FB-382
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Arun M. Umarji
Materials Research Centre, Indian Institute of Science, Bangalore
Nanostructurization of Transition Metal Silicides for High Temperature Thermoelectric Applications.
22 Aug. 2014 (Friday)
4 pm
FB-382
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Harshawardhan Wanare
Department of Physics, IIT Kanpur
Can Polarization be a high-precision spectroscopic tool?
08 Aug. 2014 (Friday)
4.00 pm
FB-382
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Prof. Anandmayee Tej
Indian Institute of Space Science and Technology
Probing high-mass star formation with multi-wavelength
observations
11 April, 2014, Friday
4 pm
FB-382 |
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Prof. Sayan Kar
IIT Kharagpur
A century of extra dimensions
28 March, 2014, Friday
4 pm
FB-382 |
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Prof. Tirthankar Roy Choudhury
NCRA, Pune
Probing the Universe through Neutral Hydrogen
14 February, 2014, Friday
4 pm
FB-382 |
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Prof. R. P. Singh
PRL Ahmedabad
Hanbury Brown Twiss Experiment: Intensity Correlations in Scattered Optical Vortices
7 February, 2014, Friday
4 pm
FB-382 |
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Prof. Kaushik Bhattacharya
IIT Kanpur
Astrophysical properties of Bertrand spacetime
31 January, 2014, Friday
4 pm
FB-382
In classical mechanics Bertrand's theorem specifies the kind of potentials which can give rise to closed, stable circular orbits. One can generalize the results of Bertrand's theorem in special relativity where the particle moving in the potential can have high speeds. There has been a generalization of Bertrand's theorem in general relativity where one can have certain spacetimes called Bertrand spacetimes (BSTs). From each point on the spatial hypersurface of a BST there can pass a closed, stable circular orbit. These spacetimes can have very interesting properties as far as galactic astrophysics is concerned. The talk will focus on the astrophysical properties of BSTs and will particularly focus on the issues concerning velocity rotation curves and the dark-matter source which can seed such a spacetime. |
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Prof. T. R. Seshadri
Delhi University
Learning about the Universe through the Cosmic Microwave Background Radiation
17 January, 2014, Friday
4 pm
FB-382
We are surrounded by a bath of radiation which is of primordial origin. This radiation is coming from all directions. It has a nearly blackbody spectrum with its peak at 160.2 GHz which is in the microwave region. Hence the name the Microwave Background radiation. Several physical processes during the course of the evolution of the Universe leave their imprint on this radiation in the form of anisotropy, polarization and deviation from the Planck Spectrum. This talk will focus on some of these features and what it can teach us about these physical processes. Particular focus will be on the effect of Cosmic Magnetic fields. |
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Prof. Mishkatul Bhattacharya
Rochester institute of Technology, Rochester, NY USA
Chiral symmetries associated with angular momentum
10 January, 2014, Friday
4 pm
FB-382
In quantum mechanics, symmetries are usually associated with physical observables which commute with the system Hamiltonian. In this talk we will discuss chiral symmetries, which anticommute with the Hamiltonian. Typically, physics students are exposed to chiral symmetries only in advanced courses, such as when they read about the Dirac equation in relativistic quantum mechanics, or when they study particle-hole symmetry in superconductivity. In this talk, we will show that chiral symmetries can be discussed in the classroom by simply using the theory of angular momentum, which is taught in virtually all introductory quantum mechanics courses. Further, we will demonstrate that while chiral symmetries cannot be associated with conserved quantities, they nonetheless simplify, and sometimes render analytically solvable, the underlying Hamiltonian. Finally, we will present as an example our recent exact solution of the effective Hamiltonian of the
ground state of the OH molecule in combined electric and magnetic fields [1].
[1] M. Bhattacharya, Z. Howard and M. Kleinert, Phys. Rev. A 88, 012503
(2013).
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Prof. Dilip Kanhere
University of Pune
Clusters at Finite Temperature: Size sensitive melting, Influence of geometry, higher than bulk melting temperatures and glassy behavior.
15 November, 2013, Friday
4 pm
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Prof. Uma Sankar
IIT Mumbai
Life of Nu
8 November, 2013, Friday
4 pm
FB-382 |
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Prof. P. Ravindran
Central University of Tamil Nadu
Application of Solar Thermal Energy - Recent Developments
1 November, 2013, Friday
4 pm
FB-382 |
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Prof. Sudeshna Sinha
IISER, Mohali
Dynamically Rewired Networks
18 October, 2013, Friday
4 pm
FB-382
We will first discuss broad classes of models of complex systems in general, and complex networks in particular. Then we will go on to show how spatiotemporal chaos in networks with strongly chaotic nodal dynamics can be tamed by dynamically changing links. Specifically, we will illustrate the results in examples ranging from neuronal networks to disease spreading models. |
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Prof. Indra Dasgupta
Indian Association for the Cultivation of Science
First Principles Calculations: The glue that binds materials, models and mechanism.
4 October, 2013, Friday
4 pm
FB-382
First principles electronic structure calculations based on density functional theory have emerged as a successful method in understanding and predicting properties of diverse class of materials. Often such calculations provide crucial insights into novel properties of materials either by themselves or in conjunction with experiments. In the present talk, we shall illustrate the usefulness of such calculations considering several examples ranging from low dimensional quantum spin systems to nanomaterials. As a first example, we shall discuss the electronic structure of the improper multiferroic, FeTe2O5Br where ferroelectricity (FE) is induced by an inversion symmetry breaking magnetic ordering resulting in strong coupling between the two order parameters. We show that the system, FeTe2O5Br is rather unique where exchange striction in the magnetically ordered state promotes polarizable Te4+ lone pair to develop ferroelectric polarization. Next we shall explain the electronic structure of the spin gap compound Sr2Cu(BO3)2 and illustrate that a careful analysis of the electronic structure is important for the identification of the correct low energy model Hamiltonian for this system. The validity of the proposed model is checked by calculating the magnetic susceptibility as a function of temperature and magnetization both as a function of temperature as well as field using quantum Monte Carlo technique and comparing them with the available experimental data. Finally we show the importance of ligands in controlling the crystal structure of nano-systems. Recently, with the aid of careful experiments it was shown that CdS nanocrystals can be thermodynamically stabilized in both wurtzite and zinc-blende crystallographic phases at will, just by the proper choice of the capping ligands. Our theoretical calculations not only provide an understanding of the mechanism but also make predictions that can be tested by experiments. |
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Prof. Mohammad Sami
JMI, New Delhi
Cosmic acceleration: dark energy and beyond.
23 August, 2013, Friday
4 pm
FB-382 |
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Prof. Nirmal Viswanathan
University of Hyderabad
Singular and Topological Optics
14 August, 2013, Wednesday
4 pm
FB-382
Singularities are an integral part of the physical world, from cosmology to quantum world, from fluid dynamics to optical physics. The most interesting aspect of the singularity is the universality of the topological structures which are independent of the physical system, reflecting the fact that the underlying physical phenomena are common to all branches of physics and science in general.
The topological connections in complex fields provide a quantitative understanding of how the skeleton structures are formed, connected and are related to physical quantities. Topological representation of complex tensor and vector flow fields provide a very useful visualization tool in engineering, medicine, soft active matter and in
several branches of physics. I will present our endeavor in this emerging area of optical physics, connecting the points of scalar, vector, and tensor wave fields with singular lines which includes wave dislocations, optical vortices and polarization singularities.
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Dr. Sourish Basu
SRON Netherlands Institute for Space Research, Utrecht, Netherlands
Can we detect carbon cycle anomalies from satellites?
8 August, 2013, Friday
4 pm
FB-382
To quantify the carbon cycle and estimate its climate response in the future, we need to understand its mechanisms in the present. One way to estimate the surface sources and sinks of carbon is to derive those from observed atmospheric gradients of carbon-containing gases such as CO2, CO and CH4. Those estimates are only as accurate as the density of the observing network, which is low over some of the most ecologically interesting areas of the planet. To bridge this gap, we can use satellites for observation, which come with their own challenges. I will describe how we can use satellites to quantify the carbon cycle, and show some results demonstrating the added value of satellite data over the existing surface observation network. |
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Prof. Tapobrata Sarkar
IIT Kanpur
Gravitational lensing, or what General Relativity can teach us about galaxies.
2 August, 2013, Friday
4 pm
FB-382 |
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Prof. Dilip Angom (PRL, Ahmedabad)
Dynamics of binary mixtures of quantum liquids in the phase
12 April, 2013, Friday
4 pm
FB-382 |
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Prof. Prasad Perlekar (TIFR, Hyderabad)
Turbulence induced coarsening arrest in binary mixtures
5 April, 2013, Friday
4 pm
FB-382
Turbulence is ubiquitous and is known to strongly enhance mixing and transport in fluids. A scalar dispersed in a turbulent flow continuously undergoes stretching and folding and mixes on time and spatial scales much shorter than what a purely diffusive mixing would predict. The enhanced mixing of turbulence can be associated to the fact that it excites fluctuations at all the length and time scales and is understood, by means of simple dimensional arguments, in terms of an scale- dependent eddy-viscosity $ν_t(l) ∼ ν(l/η)^4/3$ (for inertial scales l > η, and hence $ν_t$ > ν). In many cases, turbulent flows involve more than one phases such as liquid-liquid or gas-liquid mixtures. As a simple example of such a system one can think of turbulence in binary mixtures.
When a binary mixture is cooled below its critical temperature it undergoes a phase transition and the mixture separates into its individual components. This phenomenon is widely known as spinodal decomposition. Theoretically, the temperature below which the system undergoes the phase transition is determined by finding out the point where the free-energy minimum becomes degenerate. The dynamics of the phase separation can be modeled by means of the Navier-Stokes equations coupled to a Cahn-Hilliard or model-B equations.We first review various regimes of coarsening process in binary
mixtures. Coarsening process leads to demixing of phases whereas, turbulence enhances mixing. We study the interplay of these two competing mechanisms the result of which is to arrest the coarsening process. The suppression of coarsening is quantified by the so called coarsening length scale which ceases to grow in presence of turbulence. Finally we also show that the dimensional estimate of Hinze, to predict droplet breakup, can be also used to estimate the coarsening length in presence of turbulence.
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Prof. Banibrata Mukhopadhyay (IISc, Bangalore)
New mass limit for white dwarfs: Need to revisit expansion history of Universe?
21 March, 2013, Thursday
4 PM
FB 382
Chandrasekhar in his celebrated work showed that the maximum mass of white dwarfs is 1.44 solar mass. In this talk, I will first show that the generic mass limit of white dwarfs is 2.58 solar mass, when white dwarfs are (highly) magnetized. The limiting mass of white dwarfs is responsible for type Ia supernovae which in turn are related to our understanding of the expansion history of the Universe.Then the question is, whether or not the new mass limit affects our understanding of this expansion rate which is based on Chandrasekhar's limit. Indeed, the new mass limit helps in explaining several peculiar, over-luminous supernovae. I will attempt to discuss these issues.
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Prof. Vishwesha Guttal (IISc, Banglore)
Sync to safety: Coordinated collective movement leads to reduced predation risk
14 March, 2013, Thursday
5 PM
FB 382
The physics of coordinated collective movement in animal groups have long fascinated physicists. The non-equilibrium statistical physics approach of physicists has helped us understand how microscopic interactions can lead to spectacular macroscopic collective dynamics in animal groups. However, we do not yet have a clear understanding of why do organisms display such motion. In this talk, I will present how we can combine the interacting particle models of collective movement with
game theory to obtain key insights into why organisms exhibit collective synchronized movement. In particular, I will discuss our recent results on how predation and, counter intuitively, cannibalism can favour organisms that exhibit social behaviour.
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Prof. Yogesh Saxena (Institute for Plasma Research, Gandhinagar)
Nuclear Fusion: ITER & Beyond
8 March, 2013, Friday
4 PM
FB 382 |
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Prof. Surajit Dhara (University of Hyderabad)
Temperature driven discontinuous surface anchoring transitions in liquid crystals
1 March, 2013, Friday
4 PM
The orientation of liquid crystals on chemically treated surface is of great importance for understanding the interfacial phenomena as well as technological applications. In liquid crystal displays commonly two
types of molecular orientations are exploited namely, parallel (or planar) and vertical, and these orientations are stable over a wide range of temperature. The talk deals with the orientational properties of some common liquid crystal phases on perfluoropolymer treated surfaces. We show a new orientational (anchoring) transition in liquid crystals with a large thermal hysteresis. A simple theoretical model is developed to understand the effect of electric field on this transition. We demonstrate a novel rewritable memory device utilizing the hysteresis. Finally we show that laser-driven microflow-induced bistable orientation can be useful for various applications.
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Prof. Sanjay Puri (JNU)
Cooling and Brownian Motion in Viscoelastic Granular Gases
15 February, 2013, Friday
4 PM
FB 382
We discuss freely-evolving granular gases. This system loses energy (cools) continuously because of the inelastic collisions between particles. The system initially cools in a homogeneous cooling state (HCS), but a clustering instability drives it into an inhomogeneous cooling state (ICS). We present results for the HCS and ICS of granular gases where (a) the restitution coefficient is constant; (b) the restitution coefficient depends on the relative collision velocity.
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Prof. Amitava Sen Gupta ( National Physical Laboratory, N. Delhi)
What is an Atomic Clock and how accurate can it be?
8 February, 2013, Friday
4 PM
FB 382
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Prof. Dharam Vir Ahluwalia, State University of Campinas (Brasil) and University of Canterbury (New Zealand)
Origin of Darkness of Self-Interacting `Elko' Dark Matter
18 January, 2013, Friday
4 PM
FB 382
I will very briefly review construction of Dirac and Maxwell equations, and having done that I'll proceed to introduce an unexpected theoretical discovery of a matter that is fermionic, spin 1/2, and yet does not satisfy Dirac equation. I'll then argue that it is perhaps the
sought after dark matter.
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Prof. Tarun Souradeep
IUCCA
Revealing experimental beam distortions from CMB maps
28th Dec, 2012, 4 pm
FB 382 |
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Prof. Charles Reichhardt
Theoretical division, Los Alamos National Laboratory, USA
Jamming and clogging transitions for systems with quenched disorder
29th Nov, 2012, 4 pm
FB 382 |
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Dr. Gopal Dixit
Center for free-electron laser science Hamburg, Germany.
IX-ray in fourth dimension
27th Nov, 2012, 12 Noon
FB 382 |
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Prof. Tejinder Singh
TIFR Mumbai
Is Quantum Theory exact, or approximate?
16th Nov, 2012, 4 PM
FB 382 |
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Prof. Mandar M. Imamdar
IIT Mumbai
Modelling collective cell migration in epithelial sheets: how far can simple mechanics take us?
9th Nov, 2012, 4 PM
FB 382 |
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Prof. Manoranjan Khan
Jadavpur University, Jadavpur
Hydrodynamical Instabilities in Astrophysics and Inertial Confinement Fusion
1st Nov, 2012, 5 PM
FB 382 |
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Prof. Shobhana Narasimhan
JNCASR
Designing novel materials from first principles
18th Oct, 2012, 5 PM
FB 382 |
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Prof. Bimalendu Deb
IACS Kolkata
Atom-molecule coherence: new physics with cold molecules
5th Oct, 2012, 4 PM
FB 382 |
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Dr. R Vijaya
IIT Kanpur
Fiber lasers – versatile technology for multiple applications
3rd Oct, 2012, 5:30-6:30 PM
SL 215
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Prof. Tapan K. Sengupta
IIT Kanpur
A deterministic route to turbulence from receptivity stage.
27 January, 2012, Friday
4 pm
FB-382
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Prof. Tarun Kanti Ghosh
IIT Kanpur
Magnetotransport properties of a two-dimensional electron gas with spin-orbit interaction
23 January, 2012, Monday
FB 382
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Prof. Satyajit Banerjee
IIT Kanpur
Exploring the coexistence of order parameters and a search for broken symmetry in the vortex state of superconductors
20 January, 2012, Friday
FB 382
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Prof. Amit Dutta
IIT Kanpur
Quantum Phase transitions: Dynamics and Fidelity
18 January, 2012, Wednesday
FB 382
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Prof. Avinash Mahajan
IIT Mumbai
NMR: A local probe of magnetism in materials
13 January, 2012, Friday
FB 382
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Prof. Gautam Sengupta
IIT Kanpur
FROM BLACK HOLES TO BOILING WATER
12 January, 2012, Thursday
FB 382
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Dr. Sagar Chakraborty
Neils Bohr Institute, Copenhagen
Effect of Composition Gradient on the Stability of Intra-Cluster Medium
6 January 2012 (Friday)
FB 382
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Prof. Rupamanjari Ghosh
JNU
Optical manipulation of bulk matter at room temperature using quantum mechanics
18 November, 2011, Friday
FB 382
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Prof. Sumathi Rao
HRI
Topological insulators and helical edge states
9 November, Wednesday
FB 382
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Prof. Saikat Ghosh
S N Bose National Centre For Basic Sciences, Kolkata
Cavity QED: A new regime of atom-photon interactions
4 November, 2011, Friday
FB 382
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Prof. Gobinda Majumder
TIFR
The LHC machine : a new frontier in energy domain
28 October, 2011, Friday
FB 382
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Prof. Jayanta Bhattacharjee
S N Bose National Centre For Basic Sciences, Kolkata
Exotic Objects in the Kitchen Sink
21 October, 2011, Friday
FB 382
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Prof. Kalobaran Maiti
TIFR
Enigmatic magnetism - dilemma to order
14 October, 2011, Friday
FB 382
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Prof. Madhav Ranganathan
IIT Kanpur
Kinetic Monte Carlo simulations of Heteroepitaxial systems
30 September, 2011, Friday
FB 382
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Prof. Prem B Bisht
IIT Madras
Experiments on whispering gallery modes of micro-cavities: Current status and future prospects
23 September, 2011, Friday
FB 382
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Prof. Sushil Mujumdar
TIFR
Modes of a disordered medium with amplification
9 September, 2011, Friday
FB 382
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Prof. Kandaswamy Subramanian
IUCAA, Pune
Magnetizing the universe
26 August, 2011, Friday
FB 382
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Prof. V. Subrahmanyam
IIT, Kanpur
How entangled is a quantum many-body state? The Quantum Superposition Ways of Waves
19 August, 2011, Friday
FB 382
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Prof. Pushan Ayyub
TIFR, Mumbai
A Journey into Nanoworld in a vehicle made of Niobium
11 August, 2011, Thursday
FB 382
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Prof. Harshawardhan Wanare
IIT, Kanpur
Revisiting Optical Bistability: a new twist to an old story!
5 August, 2011, Friday
FB 382
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Prof. Santosh Ansumali
Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore
Kinetic Schemes for the Fokker-Plack Equation
29 October, 2010, Friday
FB 382
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Speaker: Prof. Arnab Rai Choudhuri
IISc, Bangalore
Can we predict sunspot cycles?
22 October, 2010, Friday
FB 382
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Prof. Sukanta Panda
IISER, Bhopal
Detecting cosmic rays from high to ultra high energies
1 October, 2010, Friday
FB 382
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Prof. K. R. Sreenivas
Jawaharlal Nehru Center for Advanced Scientific Research, Bangalore
An experimental study of mantle convection
17 September, 2010, Friday
FB 382
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Prof. R. Vijaya
IIT Kanpur/IIT Mumbai
Laser action in optical fibers and photonic crystals
10 September, 2010, Friday
FB 382
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Dr. Krishnacharya
IIT Kanpur
Harnessing elastic instabilities in soft matter
6 September, 2010, Monday
FB 382
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Prof. Subroto Mukerjee
IISC Bangalore
Thermoelectricity: Relations and correlations
3 September, 2010, Friday
FB 382
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Prof. Rajeev Gupta
I.I.T. Kanpur
Experimental Investigations on Single Crystals and Thin films ofMultiferroics
1 September, 2010, Wednesday
FB 382
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Dr. S. Dhamodaran
I.I.T. Kanpur
Interaction of charged particles with matter: Design and controlof materials
31 August, 2010, Monday
FB 382
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Prof. Mahendra K. Verma
I.I.T. Kanpur
Field Reversals in Convection and Dynamo
27 August, 2010, Monday
FB 382
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Prof. S. A. Ramakrishna
I.I.T. Kanpur
Focusing and concentrating light at the nanoscale
20 August, 2010, Friday
FB 382
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Prof. K. P. Rajeev
I.I.T. Kanpur
Nanoparticle Magnetism
13 August, 2010, Friday
FB 382
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Prof. Pratik Khastgir
I.I.T. Kharagpur
Boundary value problems for the Helmholtz equation
9 April, 2010, Friday Time: 4 PM
FB 382
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Tanusri Saha-Dasgupta
S. N. Bose. National Center for Basic Sciences
Understanding Physics and Chemistry of Complex Materials: From First-principles Calculations to Materials Modeling
26 March, 2010, Friday Time: 4 PM
FB 382
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Prof. Parthasarathi Majumdar
Saha Institute of Nuclear Physics, Kolkata
Holography, gauge gravity connection and black hole entropy
12 March, 2010, Friday Time: 4 PM
FB 382
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Prof. Parongama sen
University of Kolkata
Dimensionality, Statistical Physics and Complex networks
26 February, 2010, Friday Time: 4 PM, tea @ 3:45 PM
FB 382
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Prof. Avinash Khare
IOP, Bhubaneshwar
Solution in Search of a Problem
19 February, 2010, Friday, Time: 4 PM, tea @ 3:45 PM
FB 382
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Prof. D. P. Roy
TIFR
Basic Constituents of Matter - Visible and Invisible
12 February, 2010, Friday, Time: 4 PM, tea @ 3:45 PM
FB 382
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Prof. Douglas Osheroff (1996 physics Nobel Laureate)
Stanford University
What really happens at absolute zero?
12 February, 2010, Friday, Time: 10 AM
Outreach Auditorium
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Prof. Suresh Govindarajan
I.I.T. Chennai
Understanding black hole entropy in string theory
22 January, 2010, Friday, Time: 4 PM, tea @ 3:45 PM
FB 382
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Prof. Krishnacharya
I.I.T. Kanpur
Investigation of interfacial properties e.g. wetting, adhesion and friction of topographically structured substrates
15 January, 2010, Friday
FB 382
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Prof. Siddharth Ramachandran
Boston University
Non-Zero-Order Light: Beams that can do what a Gaussian cannot
18 November, 2009, Wednesday
FB 382
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Prof. Sudeshna Sinha
Institute of Mathematical Sciences, Chennai and IISER Mohali
EXPLOITING CHAOS
6 November, 2009, Friday
FB 382
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Speaker:
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Prof. Tapobrata Sarkar
I.I.T. Kanpur
Branes meet Dimers - New Directions and Perspectives in String Theory
23 October, 2009 at 4 pm (Postponed)
FB 382
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Speaker:
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Prof. Mahendra K. Verma
I.I.T. Kanpur
Bifurcations and Chaos in Rayleigh Benard Convection
9 October, 2009 at 4 pm
FB 382
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Dr. Subir K. Das
Jawaharlal Nehru Centre for Advanced Scientific Research
Finite Size Effects and Criticality: Some Recent Stories
18 September, 2009 at 4 pm
FB 382
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Speaker:
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Dr. Mary Michael
IIT Kanpur
Aerosols in atmospheres
11 September, 2009 at 4 pm
FB 382
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Prof. R. K. Kotnala
NPL, N. Delhi
Magnetic Materials R & D and International Traceability of their Measurement at NPL
4 September, 2009 at 4 pm
FB 382
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Speaker:
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Prof. Rajiv Singh
University of California at Davis
Protein misfolding: mad--cows and prions
August 28, 2009 at 4 pm
FB 382
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Dr. Palash B. Pal
Saha Institute of Nuclear Physics, Kolkata
Measurement of Length
August 21, 2009 at 4 pm
FB 382
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Speaker:
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Dr. Gautam Sinha
R. R. Center for Advanced Technology, Indore
Design of Magnets for Synchrotron Radiation sources
August 7, 2009
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R. Vijaya
IIT Bombay
Advanced optical functionalities in Photonic crystals
April 16, 2009
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Speaker:
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Swapan K. Ghosh
BARC, Mumbai
Concept of Density and Materials Modelling at Different LengthScales
April 9, 2009
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S. B. Roy
RRCAT, Indore
Metamagnetic materials and magnetic-glass
April 2, 2009
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Speaker:
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Kedar Damle
TIFR, Mumbai
Surprises in magnets without net moments
March 26, 2009
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Speaker:
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Srikanth Sastry
JNCASR, Bangalore
Slow dynamics and the glass transition in supercooled liquids
March 19, 2009
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Speaker:
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D. Kanjilal
Inter-University Accelerator Centre, New Delhi
Development of controlled exotic phase in solid by energetic ion beams
February 26, 2009
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Date:
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Giuseppe E. Santoro
International School for Advanced Studies (SISSA) & ICTP, Italy
Quantum annealing: recent studies
February 12, 2009
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Mandar M. Deshmukh
TIFR, Mumbai
Electron transport and electromechanical properties of individual semiconductor nanowires
January 29, 2009
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Madhav Ranganathan
Indian Institute of Technology Kanpur
Theory of Impurity Induced Step Pinning and Recovery in Crystal Growth from Solutions
January 15, 2009
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Speaker:
Institution:
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Date:
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V. Ravishankar
Indian Institute of Technology Kanpur
The Quantum way to determine the "shapes" of functions
January 1, 2009
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Speaker:
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Date:
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Dr. Banibrata Mukhopadhyay
Indian Institute of Science, Bangalore
Measuring spin of black holes in the universe:A test of General Relativity
October 30, 2008
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Speaker:
Institution:
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Date:
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Dr. Kaushik Bhattacharya
Deaprtment of Physics, IIT-Kanpur
The Legacy of Nambu, Kobayashi and Maskawa
October 27, 2008
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Institution:
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Dr. Arindam Ghosh
Indian Institute of Science, Bangalore
Intrisic magnetism in high-mobility semiconductors: a bottom-up route to spintronics?
October 23, 2008
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Speaker:
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Dr. Praveen Chaddah
UGC-DAE Consortium for Scientific Research, Indore
Glass-like metastabilities across magnetic transitions-our results and some new concepts
October 16, 2008
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Speaker:
Institution:
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Date:
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Dr. Sutapa Mukherjee
Department of Physics, IIT-Kanpur
Fixed points and boundary layers in asymmteric simple exclusion processes
September 25, 2008
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Speaker:
Institution:
Title:
Date:
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Dr. Roop Mallik
TIFR-Bombay
Single Molecule Biophysical Techniques beyond Single Molecule
September 18, 2008
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Speaker:
Institution:
Title:
Date:
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Dr. Zakir Hossain
Department of Physics, IIT-Kanpur
Interplay Between Superconductivity and Magnetism in Conventional and Unconventional Superconductors
September 11, 2008
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Speaker:
Institution:
Title:
Date:
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Professor Pinaki Majumdar
Harish-Chandra Research Institute, Allahabad
Nanoscale Textures in Correlated Electron Systems
September 04, 2008
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Speaker:
Institution:
Title:
Date:
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Shiv K. Sethi
Raman Research Institute, Bangalore
Probing Large scale structure of the universe using neutral hydrogen
August 21, 2008
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Speaker:
Institution:
Title:
Date:
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Animangsu Ghatak
Department of Chemical Engineering, IIT Kanpur
Bio-inspired patterned adhesives
August 7, 2008
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Speaker:
Institution:
Title:
Date:
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Mahendra K. Verma
IIT Kanpur
Physics of Magnetic Field Generation (Dynamo)
28 March, 2008 |
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Speaker:
Institution:
Title:
Date:
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Sanjay Puri
School of Physical Sciences, JNU, New Delhi
Inhomogeneous Cooling in Granular Gases
7 March, 2008 |
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Speaker:
Institution:
Title:
Date:
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C.V. Vishveshwara
Indian Institute of Astrophysics
BLACK HOLES : Facts, Fallacies and Fantasies
29 February, 2008 |
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Speaker:
Institution:
Title:
Date:
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Gunter M. Schuetz
Research Center, Juelich, Germany
Single-File Diffusion Far From Equilibrium
15 February, 2008 |
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Speaker:
Institution:
Title:
Date:
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Ashoke Sen
HRI, Allahabad
Black Holes in String Theory
January 8, 2008 |
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Speaker:
Institution:
Title:
Date:
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Sunil K. Gupta
T.I.F.R. Mumbai
Astroparticle Physics with the GRAPES - 3 Experiment
November 1, 2007 |
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Speaker:
Institution:
Title:
Date:
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J. K. Bhattacharjee
Indian Association for the Cultivation of Science, Kolkata
Reaction Diffusion Patterns : Classical and Quantum
October 25, 2007 |
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Speaker:
Institution:
Title:
Date:
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J. Kirschner
Max-Planck-Institut fur Mikrostrukturphysik, Weinberg
Spin-polarized Scanning Tunneling Microscopy
October 5, 2007 |
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Speaker:
Institution:
Title:
Date:
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Yogesh M. Joshi
Department of Chemical Engineering, IIT Kanpur
Ageing Dynamics in Soft Matter
September 27, 2007 |
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Speaker:
Institution:
Title:
Date:
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Anjan K. Gupta
Department of Physics, IIT Kanpur
STM studies of Electronically Inhomogeneous Surfaces
September 13, 2007 |
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Speaker:
Institution:
Title:
Date:
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C. Venkatesan
Department of Aerospace Engineering, IIT Kanpur
Challenges in Rotary Wing Vehicles
September 6, 2007 |
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Speaker:
Institution:
Title:
Date:
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Amit Roy
Inter University Accelerator Centre, New Delhi
Challenges in Accelerator Physics
August 23, 2007 |
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Speaker:
Institution:
Title:
Date:
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Zakir Hossain
Department of Physics, IIT Kanpur
Quantum phase transition in YbIr2Si2 and excitonic mass enhancement in Pr - compounds
August 16, 2007 |
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Speaker:
Institution:
Title:
Date:
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Debabrata Goswami
Department of Chemistry, IIT Kanpur
Ultrafast Pulse Shaping-from Quantum Computing to Medical Imaging
August 9, 2007 |
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Speaker:
Institution:
Title:
Date:
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D.D. Sarma
MLS Professor's Unit and Centre for Advanced Materials; Indian Association for the Cultivation of Science, Kolkata
Sr2FeMoO6 , A fascinating compound
August 2, 2007 |
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Speaker:
Institution:
Title:
Date:
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N. Nayak
S.N.B.N.C.B.S. , Kolkata
Spin Squeezing and Quantum Entanglement
April 20, 2007 |
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Speaker:
Institution:
Title:
Date:
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Krishnendu Sengupta
S. I. N. P. , Kolkata
Low dimensional and strongly correlated systems: Some recent trends
April 18, 2007 |
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Speaker:
Institution:
Title:
Date:
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S.C. Agarwal
IIT, Kanpur
A Bandwagon called Nanotechnology
April 13, 2007 |
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Speaker:
Institution:
Title:
Date:
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K.P. Rajeev
IIT, Kanpur
Magnetism of Antiferromagnetic Nanoparticles
April 05, 2007 |
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Speaker:
Institution:
Title:
Date:
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Rahul Pandit
IISc, Bangalore
The Physical Modelling of Cardiac Arrhythmias
March 30, 2007 |
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Speaker:
Institution:
Title:
Date:
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Venkat Chandrashekhar
Physics Department, Northwestern University, USA
Thermal Transport in Metallic Nanostructures
March 23, 2007 |
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Speaker:
Institution:
Title:
Date:
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A.R. Harish
IIT, Kanpur
RFID: Identification using radio frequencies
March 02, 2007 |
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Speaker:
Institution:
Title:
Date:
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Amit Dutta
IIT, Kanpur
Long-range percolation, contact processes and disorder correlation
February 23, 2007 |
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Speaker:
Institution:
Title:
Date:
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Vijay B. Shenoy
IISc, Bangalore
Electrons, Patterns and Correlations
February 09, 2007 |
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Speaker:
Institution:
Title:
Date:
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Justin Raj David
HRI, Allahabad
Black Hole Entropy in String
TheoryFebruary 02, 2007 |
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Speaker:
Institution:
Title:
Date:
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Amit Ghoshal
UCLA, USA
Toward Strong Interactions in Circular Quantum Dots: Correlation Induced Inhomogeneity
January 17, 2007 |
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Speaker:
Institution:
Title:
Date:
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Prabal Maiti
IISc, Bangalore
Nanotubes under Hydrostatic Pressure and Water Transport in Nanotubes
January 5, 2007 |
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Speaker:
Institution:
Title:
Date:
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T.K. Ghosh
JEPS, Okayama, Japan
Beautiful World of Cold Atoms
December 28, 2006 |
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Speaker:
Institution:
Title:
Date:
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Ashwini K. Sharma
Clausthal University of Technology, Germany
Fiber-optic Mid-infrared Laser Sensors for the Detection of Explosives
December 21, 2006 |
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Speaker:
Institution:
Title:
Date:
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Abhijit Sen
Institute for Plasma Research, Gandhi Nagar
Clocks, Fireflies and the Landau Damping of Plasma Waves
November 22, 2006 |
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Speaker:
Institution:
Title:
Date:
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Prakash Mathews
SINP, Kolkata
Expecting LHC: SM and Beyond
November 15, 2006 |
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Speaker:
Institution:
Title:
Date:
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Sanjay Kumar
BHU, Varanasi
Force Induced Transitions in Biopolymers
November 8, 2006 |
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Speaker:
Institution:
Title:
Date:
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Abhijit Mookerjee
IIT Kanpur / SNBNCBS, Kolkata
Density Functional Theory for Excited States
November 1, 2006 |
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Speaker:
Institution:
Title:
Date:
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Dimitri Batani
Universita di Milano Bicocca, Italy
Transport of Intense Laser Produced Electron Beams in Matter
October 30, 2006 |
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Speaker:
Institution:
Title:
Date:
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V. V. Sreedhar
IIT Kanpur
Classical Topology and Quantum Entanglement
October 27, 2006 |
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Speaker:
Institution:
Title:
Date:
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Gilbert Lonzarich
Cambridge University
Quantum tuning of Magnetic and Ferroelectric Materials
October 25, 2006 |
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Speaker:
Institution:
Title:
Date:
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Arun K. Grover
TIFR Mumbai
Phase Diagram Studies in Vortex Matter: A Perspecive
October 11, 2006 |
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Speaker:
Institution:
Title:
Date:
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Jayajit Das
MIT, USA
Early and Late Signalling Events during T-cell Activation
September 27, 2006 |
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Speaker:
Institution:
Title:
Date:
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Sumathi Rao
HRI, Allahabad
Novel Phenomena in Low Dimensional Systems
September 20, 2006 |
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Speaker:
Institution:
Title:
Date:
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A. Pramesh Rao
NCRA (TIFR), Pune
Science with GMRT
September 18, 2006 |
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Speaker:
Institution:
Title:
Date:
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M. K. Harbola
IIT Kanpur
Density Functional Theory of Ground and Excited states
September 13, 2006 |
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Speaker:
Institution:
Title:
Date:
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Tapobrata Sarkar
IIT Kanpur
Excitements in String Theory
August 30, 2006 |
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Speaker:
Institution:
Title:
Date:
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H. Wanare
IIT Kanpur
Multicolored Atomic Coherence
August 23, 2006 |
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Speaker:
Institution:
Title:
Date:
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V. Venkataraman
IISc. Bangalore
Physics of Strained Silicon-Germanium Semiconductor Heterostructures
August 9, 2006 |
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Speaker:
Institution:
Title:
Date:
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Debashish Chowdhury
IIT, Kanpur
Packers and Movers of Genetic Materials: Physics of DNA, RNA- Manipulating Nano-machines.
August 2, 2006 |
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Speaker:
Institution:
Title:
Date:
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Ashutosh Sharma
IIT, Kanpur
Self -Organized Patterning of Soft Solids: Elastic Contact Lithography
April 19, 2006 |
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Speaker:
Institution:
Title:
Date:
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Deshdeep Sahdev
IIT, Kanpur
Gas Chromatographs, STMs and all that..
March 22, 2006 |
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Speaker:
Institution:
Title:
Date:
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Guruprasad Kar
ISI, Kolkata
Quantum Impossibilties Turn into Some Useful Tasks
March 07, 2006 |
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Speaker:
Institution:
Title:
Date:
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Akhlesh Lakhtakia
Penn. State University, USA
Negative Refraction in Outer Space
March 03, 2006 |
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Speaker:
Institution:
Title:
Date:
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Srinivas Krishnagopal
R R Center for Advanced Technology, Indore
Terahertz and X-ray Lasers
February 22, 2006 |
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Speaker:
Institution:
Title:
Date:
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B. N. Dwivedi
IT BHU, Varanasi
Physics Laboratory in the Sky
January 25, 2006 |
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Speaker:
Institution:
Title:
Date:
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Mahendra. K. Verma
Indian Institute of Technology, Kanpur
Universal Scaling Laws for Driven Non-Equilibrium Systems
January 18, 2006 |
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Speaker:
Institution:
Title:
Date:
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Harshawardhan Wanare ,Debabrata Goswami
Indian Institute of Technology, Kanpur
The Nobel Prize in Physics - 2005
December 28, 2005 |
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Speaker:
Institution:
Title:
Date:
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Sudipta Maiti
Tata Institute of Fundamental Research, Mumbai
Inter Molecular Associations in Biology: A Matter of Life and of Death
November 23, 2005 |
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Speaker:
Institution:
Title:
Date:
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Chandan Dasgupta
Indian Institute of Science, Bangalore
Statistical Mechanics of Vortex Matter in Superconductors
November 16, 2005 |
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Speaker:
Institution:
Title:
Date:
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Parthasarathy Majumdar
Saha Institute of Nuclear Physics, Kolkata
The Mysterious Warmth of Black Holes
November 9, 2005 |
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Speaker:
Institution:
Title:
Date:
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Kazuaki Sakoda
National Institute for Materails Science, Tsukuba, Japan
Quantum Localization of Photons and Non-Markovian Emission in Photonic Crystals
October 26, 2005 |
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Speaker:
Institution:
Title:
Date:
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Sriram Ramaswamy
Indian Institute of Science, Bangalore
The Mechanics and Statistics of Active Matter
October 20, 2005 |
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Speaker:
Institution:
Title:
Date:
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Subhendu Ghosh
University of Hyderabad
Electrical Signalling in the Brain and the Phenomenon of Learning
October 05, 2005 |
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Speaker:
Institution:
Title:
Date:
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Gautam Sengupta
IIT Kanpur
Brane World Black Holes
October 03, 2005 |
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Speaker:
Institution:
Title:
Date:
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R. Simon
Institute of Mathematical Sciences
Some Problems Arising in Quantum Information Theory
September 28, 2005 |
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Speaker:
Institution:
Title:
Date:
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Urjit. A. Yajnik
IIT Mumbai
The New Standard Model of Cosmology and Prospects for a Unified Theory of Elementary Particles
September 19, 2005 |
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Speaker:
Institution:
Title:
Date:
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Pushan Ayyub
TIFR, Mumbai
There is plenty of SCIENCE at the bottom
September 07, 2005 |
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Speaker:
Institution:
Title:
Date:
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Ranjini Bandyopadhyay
RRI, Bangalore
Slow Dynamics and Aging in Soft Glassy Materials
August 31, 2005 |
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Speaker:
Institution:
Title:
Date:
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V.N. Kulkarni
IIT Kanpur
Nano-Science and Engineering by Ion beams
August 24, 2005 |
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Speaker:
Institution:
Title:
Date:
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V. Subrahmanyam
I I T Kanpur
How Entangled are Quantum States?
August 17, 2005 |
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Speaker:
Institution:
Title:
Date:
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S. Duttagupta
S N Bose National Centre for Basic Science, Kolkata
Memory in Magnetic Nano-particles
August 11, 2005 |
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Speaker:
Institution:
Title:
Date:
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Rama Govindarajan
JNCASR, Bangalore
The First Steps Towards Turbulence in Shear Flows
August 03, 2005 |
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Speaker:
Institution:
Title:
Date:
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Saurya Das
Univ. Lethbridge, Alberta
Is Entanglement Entropy Proportional to Horizon Area?
July 29, 2005 |
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Speaker:
Institution:
Title:
Date:
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Amita Das
Institute of Plasma Reasearch
Role of Turbulence in Fast Ignition Laser Fusion
July 28, 2005 |
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Speaker:
Institution:
Title:
Date:
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Suresh Govindarajan
IIT Madras
D-branes Solitons in String Theory
April 15, 2005 |
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Speaker:
Institution:
Title:
Date:
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Siddharth. S. Saxena
Cavendish Laboratory, University of Cambridge
Superconductivity near a Quantum Critical Point and beyond
April 08, 2005
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Speaker:
Institution:
Title:
Date:
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G. Baskaran
Institute of Mathematical Sciences, Madras
Diamond route to High Temperature Superconductivity
April 06, 2005 |
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Speaker:
Institution:
Title:
Date:
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Tarun Souradeep
IUCAA, Pune
Cosmological Principle & the Cosmic Microwave Background
April 04, 2005 |
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Speaker:
Institution:
Title:
Date:
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Madan Rao
Raman Research Institute, Bangalore and NCBS, Bangalore
Dynamics of Solid State Transformations
March 30, 2005 |
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Speaker:
Institution:
Title:
Date:
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Pinaki Majumdar
HRI Allahabad
The "DMFT revolution" in Many Body Physics
March 18, 2005 |
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Speaker:
Institution:
Title:
Date:
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Atish Dabholkar
TIFR Mumbai
Going beyond Bekenstein and Hawking — Black Hole Entropy In String Theory
March 17, 2005 |
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Speaker:
Institution:
Title:
Date:
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Geetanjali Sarkar
IITK
A Late Stage of Stellar Evolution : the Hot Post-AGB Phase
March 04, 2005 |
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