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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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