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Dr. Homi Bhabha Lectures:
(an annual event organized by IISER Pune in memory of Dr. Homi Bhabha)
November 8, 2024: Prof. Rama Govindarajan, ICTS Bangalore
Title: How dust talks to turbulence
Abstract: Air in the atmosphere and water in the ocean are often in turbulent flow. And often such flows carry particles of dust, snow, living things, various debris and water droplets. We will start by discussing a sphere falling under gravity in quiet fluid and build from there on to slightly more complicated situations encountered in dusty flows. We will try to see why studying these flows could be important.
November 16, 2023: Prof. Sudeshna Sinha, IISER Mohali
Title: Harnessing Chaos
Abstract: The concept of Chaos represents a new and open frontier of the old field of Classical Mechanics. We will indicate some of the challenges in characterization, prediction and control of classical chaos. We will then go on to discuss the opportunities offered by such complex systems and directions for exploiting the richness of chaotic dynamics for applications.
November 21, 2022: Prof. Umesh V Waghmare, JNCASR, Bengaluru, India
Title: Instabilities of Crystals and their Functional Behaviour
Abstract: Properties of a crystalline material are fundamentally determined by its electronic and atomic structure. Some crystals host instabilities that cause sharp changes in the structure with temperature or external fields while preserving their rigidity. Symmetry breaking at such a structural transition is often responsible for the emergence of the material’s technologically important functional properties. For example, applications of a ferroelectric crystal in sensors, speakers, heartbeat monitors or in memories are possible due to its functional properties of piezoelectricity and electrically switchable dipoles, which emerge from the broken inversion symmetry of the structure at a ferroelectric transition caused by an instability of a polar phonon. Functional properties of advanced materials have their roots in various such incipient instabilities. In this talk, I present the First-principles theoretical approach based on fundamental laws of Physics that can be used in identifying such instabilities in crystals and development of simple effective models that capture interactions between the instabilities and external forces, enabling prediction of material-specific functional behaviour of advanced materials. This approach relies on computer simulations and guides experimental efforts towards development of novel materials and devices. We illustrate it in the context of crystal instabilities that are relevant to functional properties of ferroelectrics, thermo-electrics and shape memory alloys, which have numerous technological applications.
December 3, 2021: Prof. Alessandra Buonanno, Max Planck Institute for Gravitational Physics, Germany
Title: What Gravitational Waves Tell Us About the Universe. [Video]
Abstract: In 2015 the LIGO detector observed, for the first time, a gravitational wave passing through the Earth produced by the collision of two black holes. Such an event was a milestone for astrophysics and it provided a spectacular confirmation of Albert Einstein’s general theory of relativity. Since then, 90 gravitational waves have been observed by the LIGO and Virgo experiments. In this lecture, I will discuss how those novel astronomical messengers are already unveiling distinctive and puzzling properties of the most peculiar astrophysical objects in the universe: black holes and neutron stars. In the next decades, those sounds of silent will provide us with the unique and wondrous opportunity of peering back to the time the first stars formed, and eventually to the very earliest moments of the universe, shedding light on its origin.
November 6, 2020: Prof. Rainer Blatt, University of Innsbruck, Austria
Title: The Quantum Way of Doing Computations
Abstract: Since the mid-nineties of the 20th century, it became apparent that one of the centuries’ most important technological inventions, computers in general and many of their applications could possibly be further enhanced by using operations based on quantum physics. Computations, whether they happen in our heads or with any computational device, always rely on real physical devices and processes. Data input, data representation in a memory, data manipulation using algorithms and finally, data output require physical realizations with devices and practical procedures. Building a quantum computer then requires the implementation of quantum bits (qubits) as storage sites for quantum information, quantum registers and quantum gates for data handling and processing as well as the development of quantum algorithms.
In this talk, the basic functional principle of a quantum computer will be reviewed. It will be shown how strings of trapped ions can be used to build a quantum information processor and how basic computations can be performed using quantum techniques. The quantum way of doing computations will be illustrated with analog and digital quantum simulations. Ways towards scaling the ion-trap quantum processor will be discussed.
October 25, 2019: Prof. Yashwant Gupta, National Centre for Radio Astrophysics (TIFR), Pune
Title: Probing the Universe using Radio Waves: from Sir J.C. Bose to modern times
Abstract: The demonstration of how to transmit and receive radio waves, first made by Sir J.C. Bose in 1895, opened up a new window to the Universe. In this talk, we will trace the fascinating story of Radio Astronomy, it's linkages to the early days of radio technology, and it's present status as a frontline tool for probing the mysteries of the Cosmos, including the cutting edge technologies and signal processing concepts involved. Special emphasis will be on the growth and current status of work in this field in India, including frontline facilities like the GMRT.
November 15, 2018: Prof. Ram Ramaswamy, JNU, New Delhi
Title: Chance ki baat hai : How complexity arises in dynamical systems
Abstract: Chance is crucial in a diverse range of situations. To paraphrase Monod (1971), nature relies on chance and not on destiny. Depending on the context, chance can mean different things to different people. A chance event may either be a consequence of intrinsic fluctuations, or may-be due to incomplete or imprecise knowledge. The notion of contingency is closely tied into that of chance, and thus uncovering the underpinnings - whether this is due to underlying stochastic phenomena or underlying chaotic dynamics - is of great interest.
Using examples from dynamical systems theory, I will discuss the role of chance when there are several coexisting dynamical attractors, with attractor basins that are intermingled in a complex manner. Small uncertainties in determining the initial state can lead to very large uncertainties in the outcomes. Intrinsic noise, on the other hand, plays a major role in small systems where the dynamics is stochastic.
Both phenomena occur in biological systems and are exploited, at a systems level, in different ways. On the one hand, chance provides the possibility of complex dynamical states such as chimeras, and on the other, chance allows for stochastic switching both in the realm of dynamics within a cell or within a population.
November 14, 2017: Prof. Subir Sachdev
Title: Strange Metals and Black Holes
Abstract: A strange metal is a new state of matter, formed by electrons in many modern materials. In this state, the electrons quantum entangle with each other across long distances, and conduct electric current collectively (rather than one-by-one, as in ordinary metal like copper). As they are cooled, most strange metals also become superconductors at relatively high temperatures, in which electric current flows with zero resistance. Black holes are stars so dense that even light is not able to escape their gravitational attaraction. Remarkably, there is an equivalance between the quantum theories of these very different physical systems: strange metals and black holes. I will illustrate this equivalance with a very simple model of a strange metal, which can also be viewed as a theory of primitive black hole.
November 9, 2016: Prof. H. R. Krishnamurthy, IISC Bangalore
Title: The Fascinating World of Ultra Cold Atoms in Optical Lattices
Abstract: In 1982 Richard Feynman proposed the concept of a ``quantum analogue simulator'', with one “designer” quantum system emulating the properties of another physical system. Amazing technological advances in laser-cooling and trapping of atoms and ions using their interaction with electromagnetic fields, especially optical lattices, (recognized by 3 Nobel Prizes,) are now bringing Feynman’s vision close to realization. Such ``optical lattice emulators'' may some day guide the development of novel materials, shed light on poorly understood phenomena in materials science, and elucidate interesting and hard to understand quantum effects in nature such as high-Tc superconductivity and quantum phase transitions. In my lecture I will review, at as non-technical a level as possible, some of the fascinating physics involved in these advances, and discuss their implications for our understanding of quantum matter, possibilities for quantum computers, etc.
November 2, 2015: Prof. Amol Dighe, TIFR, Mumbai
Title: The Changing Flavours of Neutrinos: The Journey to Nobel 2015 and Beyond
Abstract: Extraordinary puzzles need extraordinary solutions. The Physics Nobel Prize 2015 was given for solving two such extraordinary puzzles, which were set by the intriguingly invisiblea particles called neutrinos, produced inside the Sun and in the Earth's atmosphere. The solutions involved a mixture of particle physics, astrophysics, and quantum mechanics in action over large distances. They firmly established how the Sun shines, and forced us to go beyond the Standard Model of particle physics. In this talk, I shall trace the journey of neutrinos from their discovery to the solutions of these puzzles. I shall describe our current understanding of the nature of neutrions, and try to convey the excitement in the growing field of neutrino physics, astrophysics and cosmology.
November 18, 2014: Prof. Valery Rubakov
Title: The Universe Before the Hot Big Bang
Abstract: It is known for long time that the Universe went through the hot Big Bang stage, with extraordinarily high temperatures of matter and extremely rapid expansion of space. It is less known that existing observational data strongly suggest that the hot Big Bang stage was not the first one, but was preceded by yet another epoch with completely different-and unusual- properties.
The best guess for that early epoch is cosmic inflation, but alternative theories are not yet ruled out. It is reassuring that future cosmological observations will most likely be capable of unveiling the nature of the earliest epoch and physics that governed the Universe at that time.
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