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Thursday, 04 January 2018
Time Speaker Title Resources
09:30 to 10:00 Rajesh Gopakumar Welcome Address: ICTS at TEN Inauguration
10:00 to 10:30 David Gross Truth and the Scientific Method
10:30 to 11:00 -- Tea Break
11:00 to 11:30 Sankar Das Sarma Majorana 'Particle' in Condensed Matter Systems

I will describe the world-wide research efforts led by Microsoft Corporation to build a fault-tolerant topological quantum computer using non-Abelian Majorana zero modes in solid state systems. These Majorana particles are their own anti-particles as envisioned by Ettore Majorana a long time ago in the context of particle physics, and are predicted to exist as exotic bound states in the energy gap of topological superconductors. Recent experiments have observed telltale signatures of the physical existence of these Majorana particles in semiconductor-superconductor hybrid nanowires.

11:30 to 12:00 Leon Balents A Strongly Correlated Metal Built from Sachev-Ye-Kitaev Models

Strongly correlated metals comprise an enduring puzzle at the heart of condensed matter physics. Commonly a highly renormalized heavy Fermi liquid occurs below a small coherence scale, while at higher temperatures a broad incoherent regime pertains in which the quasi-particle description fails. Despite the ubiquity of this phenomenology, strong correlations and quantum fluctuations make it challenging to study. Here we show that the Sachdev-Ye-Kitaev model of a strongly interacting ""quantum dot"" can serve as the starting point to construct a soluble theory of correlated metals. This is an intriguing example of a problem originating in condensed matter physics, embraced by quantum gravity theory, and reappearing in condensed matter physics.

12:00 to 12:30 Joel E. Moore Topology and the Electromagnetic Responses of Quantum Materials

Topology and the electromagnetic responses of quantum materials This talk starts by reviewing the remarkable theoretical and experimental progress in topological materials over the past decade. Three-dimensional topological insulators realize a particular electromagnetic coupling known as “axion electrodynamics”, and understanding this leads to an improved understanding of magnetoelectricity in all materials. We then turn to how topological Weyl and Dirac semimetals can show unique electromagnetic responses; we argue that in linear response the main observable effect solves an old problem via the orbital moment of Bloch electrons, and how in nonlinear optics there should be a new quantized effect, at least approximately.

12:30 to 14:30 -- Lunch Break
14:30 to 15:00 Nathan Seiberg Quantum Field Theory as the Language of Physics

Quantum field theory (QFT) combines two of the revolutions of 20th century physics, quantum mechanics and special relativity. It is used in the description of the Standard Model of particle physics, which is tested with incredible accuracy. It is also the natural framework to describe the quantum behavior of systems with a very large number of degrees of freedom, like the electrons in a solid. In addition, QFT also plays a fundamental role in our only candidate theory of quantum gravity, String Theory. QFT has also led to deep and surprising results in mathematics. Even though QFT is so central to our understanding of physics, there are good reasons to believe that we still lack crucial insights about its underlying structure.

15:00 to 15:30 Ashoke Sen Developments in Superstring Perturbation Theory

String perturbation theory is an old subject, but some of the issues have only been resolved recently. In this talk I shall give a non-technical introduction to the subject and then describe the recent developments.

15:30 to 16:00 -- Tea Break
16:00 to 16:30 William Bialek Precision and Emergence in the Physics of Biological Function

Life is more than the sum of its parts: functions crucial for life emerge from interactions among hundreds or thousands of microscopic components. Less obvious, perhaps, is that the mechanisms of life are extraordinarily precise: our visual system counts single photons, many signaling systems are limited by the random arrivals of individual molecules, and more. Observations of extreme precision suggest a theoretical framework in which biological systems have been exquisitely tuned, optimizing performance in the presence of physical constraints. Observations of emergence suggest a different theoretical framework, in which functional behaviors are collective, and hence perhaps insensitive to microscopic details. I will give examples of both approaches, in systems ranging from a developing embryo to large networks of neurons, and from computation in the visual system to flocks of birds. At the end I will try to reconcile the two points of view. I hope to make clear why I believe that a more unified, and unifying, theoretical physics of biological systems is within reach.

16:30 to 17:00 Sriram Ramaswamy Living and Driven Matter

Active matter, in which sustained energy transduction breaks detailed balance at the scale of the constituent particles, is a key ingredient in the physicist's answer to the question ""What Is Life?"" It is also an area of intense interest in nonequilibrium physics, yielding insights into mechanics and statistics in living matter and its imitations from subcellular to oceanic scales. My talk will present selected results from recent theoretical and experimental work with colleagues and students on order, fluctuations, topological defects and entropy production in active systems.

17:00 to 17:30 Jonathon Howard Microtubules, Motors and Morphogenesis

Microtubules, motors and morphogenesis Joe Howard, Yale University The Howard lab is fascinated by the question of how small molecules like proteins, lipids and nucleotides self-assemble into cells and tissues that are thousands to millions of times larger than molecular dimensions. How do the molecules know whether the structures that they have made are the right size and shape, and localized correctly within the cell? We are approaching these questions in the context of the microtubule cytoskeleton, which underlies the morphology and movement of eukaryotic cells. Using high-resolution and single-molecule techniques, we trying to trying to understand the interaction rules that allow molecules to work together to form highly organized, yet dynamic cellular structures. I will illustrate the principles using examples from cell division, cilia-driven movement and neuronal branching morphology.

Friday, 05 January 2018
Time Speaker Title Resources
09:30 to 10:00 Manjul Bhargava How often does a polynomial take squarefree values?

A whole number is called squarefree if its prime factorization contains no repeated factors (i.e., if it is not divisible by any square number other than 1). It is well known that the density of integers that are squarefree is $6/\pi^2$, giving one of the more intriguing occurrences of $\pi$ where one might not a priori expect it!
A natural next problem that has played an important role in number theory is that of understanding the density of squarefree values taken by an integer polynomial. We survey a number of recent results on this problem - some of which use the famous ``ABC Conjecture'' and some of which do not.

10:00 to 10:30 Mahan Mj Geometry of Surface Group Representations

The classical study of surfaces establishes a correspondence between their complex geometry, algebraic geometry and differential geometry (constant curvature metrics). The space of such structures is parametrized by Teichmuller space which can be thought of as equivalence classes of discrete faithful representations of the fundamental group of a closed surface $S$ into the simplest semi-simple Lie group $SL(2,\mathbb{R})$. When we replace $SL(2,\mathbb{R})$ by $SL(2,\mathbb{C})$ we obtain the Ahlfors-Bers-Thurston theory of hyperbolic three manifolds homeomorphic to $S \times \mathbb{R}$. The analogous theory for other semi-simple Lie groups, $SL(n,\mathbb{R})$ and $SL(n,\mathbb{C})$ is undergoing rapid development with connections to dynamics, geometric group theory, mathematical physics and complex geometry. We shall give an impressionistic account of some of these developments.

10:30 to 11:00 -- Tea Break
11:00 to 11:30 Madhu Sudan Communication Amid Uncertainty

One of the basic goals of the theory of computing is to model behaviour of ""intelligent"" systems (computers or humans). Behaviour includes ability to acquire information (or knowledge), analyzing it (or reasoning) and communicating it. The theories of Turing (universal computation) and Shannon (reliable communication) offer the foundations for this study covering much of the terrain. And the remarkable progress in the technologies of computing and communication is a testament to the success of these theories. Unfortunately this success has also exposed problems in the intersection of the two fields that neither captures adequately. In our work on ""communcation amid uncertainty"" we explore some such problems, where the ability of two communicating entities to compute allows them to acquire large *mostly* common context. The commonality of the context should enable communication to be even more efficient. On the other hand the ""uncertainty"" about the context (the fact the context is only mostly common) leads to novel mathematical questions and challenging fundamental aspects of the classical theory, such as the operational definition of entropy. In this talk we will brielfy describe some of the questions and (partial) answers in this setting communication with uncertainty.

11:30 to 12:00 Suvrat Raju The Information Paradox and Holography

The information paradox is an old puzzle that emerges from a seeming contradiction between semi-classical gravity and the unitarity of quantum mechanics. I will describe how new ideas from holography can help to sharpen this paradox. I will also describe how examining the information paradox from a holographic perspective has helped to reveal some surprising features of black hole interiors.

12:00 to 12:30 Nisheeth Vishnoi The Mathematics of Bias

Bias is an increasingly observed phenomenon in the world of machine learning (ML): From gender bias in image search, racial bias in court bail pleas, to biases in worldviews depicted in personalized news feeds. At the core, what is powering these ML application are algorithms for fundamental computational tasks such as classification, data summarization, ranking, and online learning. Such algorithms have traditionally been designed with the goal of maximizing some notion of “utility” and identifying or controlling bias in their output has not been a consideration. I will focus on the problem of data summarization and present a mathematical framework that allows for ''fair algorithms'' while maintaining their utility. Developing algorithms in this setting has led to new mathematical techniques involving polynomials and entropy, leading to advances at the core of theoretical computer science."

12:30 to 14:30 -- Lunch Break
14:30 to 15:00 David Reitze Gravitational Wave Detections by LIGO and Virgo: the Birth of a Revolution in Astronomy

Over the past two years, LIGO and Virgo have opened a new window into the cosmos through the direct detections of gravitational waves from binary black hole and binary neutron star mergers. In this presentation, I will highlight the recent LIGO-Virgo discoveries, discuss what they reveal about the high energy universe, and give a preview of what may come in the future for this new and exciting field.

15:00 to 15:30 P Ajith Physics and Astronomy from Gravitational-Wave Observations

The recent detections of gravitational-wave signals from several binary merger events by LIGO and Virgo herald the beginning of a new branch of astronomy. These observations allow us to test Einstein’s theory in the regime of extreme gravity, to study the physics of black holes and neutron stars, to probe the astrophysics of compact binaries, and to measure the cosmic expansion rate by an alternative method. Based on the observed rate of these events, we expect that a large number of merger events will be observed by LIGO and Virgo in the near future, along with other possible sources. This talk will summarize what we learned from them the recent observations of gravitational waves, and prospects for the near future.

15:30 to 16:00 -- Tea Break
16:00 to 16:30 Rama Govindarajan Raindrops, Buoyancy, the Indian Monsoon

This talk will be in two parts. In the first part I will describe a cloud, and discuss how turbulence affects droplet dynamics and how droplet inertia and growth in turn change the nature of turbulence. The second part will be about dominant spatial patterns we obtain in the Indian monsoon rainfall.

16:30 to 17:00 Abhishek Dhar Hydrodynamics and Chaos Propagation in Classical Spin Chains

The talk will discuss classical Heisenberg spin chains whose time evolution is given by Hamiltonian spin-precessional dynamics. I will first discuss the hydrodynamics of the slow fields, corresponding to conserved quantities, which provide a macroscopic description of the system. At low temperatures, we show the emergence of an additional slow field which leads to anomalous scaling of dynamical correlation functions. I will then discuss the growth and propagation of localized perturbations in this system which happens ballistically at all temperatures.

17:00 to 17:30 Nima Arkani-Hamed Spacetime, Quantum Mechanics and Positive Geometry
21:00 to 22:45 Rajesh Gopakumar, Spenta R Wadia, David Gross, Manjul Bhargava, Sankar Das Sarma, Roger Blandford, Nima Arkani-Hamed Banquet Speeches
Saturday, 06 January 2018
Time Speaker Title Resources
09:30 to 10:00 Christos H Papadimitriou The Algorithmic Lens: How the Computational Perspective is Transforming the Sciences

Computation transforms the sciences (physical, mathematical, life or social) not just by equipping them, but mainly by providing a novel and powerful perspective which often leads to unforeseen insights. Examples abound: quantum computation provides the right forum for questioning and testing some of the most basic tenets of quantum physics, while statistical mechanics has found in the efficiency of randomized algorithms a powerful metaphor for phase transitions. In mathematics, the P vs. NP question has joined the list of the most profound and consequential problems; in economics, considerations of computational complexity revise predictions of economic behavior and affect the design of economic mechanisms such as auctions. In biology some of the most fundamental problems, such as understanding the effectiveness of evolution and selection as well as how the Mind emerges from the Brain, can be productively recast in computational terms. My talk is a sequence of vignettes exemplifying this pattern.

10:00 to 10:30 Sourav Chatterjee Understanding Rare Events in Graphs and Networks

Understanding rare events in graphs and networks The mathematical theory of large deviations attempts to understand the probabilities and consequences of rare events. In spite of the growing importance of graphs and networks in the modern world, we did not have the tools to understand large deviations in graphical structures until quite recently. I will talk about the development of this new area in probability theory and its surprising implications.

10:30 to 11:00 Sanjeev Arora Can machines learn without supervision?

This talk surveys challenges in designing algorithms for unsupervised learning, which learn from data that has not been labeled by humans. (By contrast, many recent success of machine learning involve algorithms that learn from labeled data.) We introduce various approaches that have been tried, and focus on recent findings about two topics:
(i) learning to represent "meaning" of text (word embeddings, sentence embeddings)
(ii) Generative adversarial nets (GANs), and their limitations.

11:00 to 11:30 -- Tea Break
11:30 to 12:00 Shri Kulkarni The Restless Universe (and the Periodic Table)

Following the Big Bang the Universe was homogeneous in matter, energy and barren of chemistry. It is the stars which built up the periodic table. Astronomers have now identified several classes of cosmic explosions of which supernovae constitute the largest group. The Palomar Transient Factory was an innovative 2-telescope, and its successor, the Zwicky Transient Factory (ZTF), is a high tech project with gigantic CCD cameras and sophisticated software system, and squarely aimed to systematically find ""blips and booms in the middle of the night"". The speaker will talk about the great returns and surprises from this project: super-luminous supernovae, new classes of transients, new light on progenitors of supernovae, detection of gamma-ray bursts by purely optical techniques and troves of pulsating stars and binary stars. ZTF is poised to become the stepping stone for the Large Synoptic Survey Telescope.

12:00 to 12:30 Ramesh Narayan Observing a Black Hole Up Close and Personal

During the last few decades, it has become increasingly clear that the Universe is full of black holes. There are literally millions in each galaxy. Most black holes are identified and studied through the energetic radiation emitted by hot gas orbiting the holes. However, until now, astronomers have never been able to obtain a close-up image of any black hole. This is about to change. The Event Horizon Telescope (EHT), an Earth-spanning radio interferometer, is poised to obtain the first event-horizon-scale images of Sagittarius A*, the supermassive black hole at the center of our Galaxy. EHT images are predicted to show certain geometrical distortions, which will provide new tests of the relativistic space-time near a black hole. The EHT will also provide an unprecedented close-up movie of the orbiting, radiating gas near the black hole. This will open up new opportunities for the study of high energy phenomena in hot magnetized astrophysical plasmas.

12:30 to 13:00 Roger Blandford The Music of the Sphere

A very low spatial resolution, three dimensional map of the universe today is made using Planck microwave background observations and the standard model of cosmology. This map can be improved using existing and future survey data. It should prove useful for improving the accuracy of the standard model and for testing basic features of the simplest model of inflation.

13:00 to 14:30 -- Lunch Break
14:30 to 15:00 Jennifer Chayes The Unreasonable Effectiveness of Learning Neural Nets: A Statistical Physics Perspective

During the last 20 years, equilibrium statistical physics has provided a framework to understand the hardness of computation in random versions of classic problems of computer science. Recently, we have developed a non-equilibrium statistical physics theory of why neural nets work so well in practice. In this talk, I will review the equilibrium statistical physics perspective on computability, and introduce our non-equilibrium statistical physics perspective on learning neural nets.

15:00 to 15:30 Surya Ganguli A Theory of Neural Dimensionality, Dynamics and Measurement

While technological revolutions in neuroscience now enable us to record from ever increasing numbers of neurons, for the forseeable future we will still only record an infinitesimal fraction of the total number of neurons in mammalian circuits controlling complex behaviors. Nevertheless, despite operating within this extreme under-sampling limit, a wide array of statistical procedures for dimensionality reduction of multineuronal recordings uncover remarkably insightful, low dimensional neural state space dynamics whose geometry reveals how behavior and cognition emerge from neural circuits. What theoretical principles explain this remarkable success? In essence, how is it that we can understand anything about the brain while recording an infinitesimal fraction of its degrees of freedom? We develop an experimentally testable theoretical framework to answer this question. By making a novel conceptual connection between neural measurement and the theory of random projections, we derive scaling laws relating how many neurons we must record to accurately recover state space dynamics, given the complexity of the behavioral or cognitive task, and the smoothness of neural dynamics. Moreover we verify these scaling laws in the motor cortical dynamics of monkeys performing a reaching task. Overall, these results yield conceptual insights into how the complexity of neural dynamics is upper-bounded by the complexity of cognition and behavior itself.

15:30 to 16:00 Mriganka Sur The Computational Logic of Cortical Circuits

The human brain has 80 billion neurons or brain cells organized into discrete processing systems. Each neuron connects with hundreds of other neurons via thousands of connections or synapses. Yet neurons do not connect indiscriminately: synaptic connections between specific sets of neurons create specific pathways and circuits that enable the brain’s remarkable information processing capabilities and give rise to cognition. Such specificity arises during brain development, and is sharpened by plasticity and learning. Brain architectures, especially those of the cerebral cortex, are far from rigid, however. Flexible reconfigurable networks are essential for cortical dynamics underlying cognition. Specifying the underlying principles is fundamental to understanding how the brain gives rise to the mind, and ultimately to framing how biological intelligence might be created in a future generation of machines.

16:00 to 16:30 Mukund Thattai Molecular Archaeology: Using Genomes to Reconstruct Two Billion Years of Cellular Life

Molecular archaeology: using genomes to reconstruct two billion years of cellular life It has been exactly 50 years since Lynn Margulis (at the time, Lynn Sagan) proposed her famous endosymbiont hypothesis. It is now well established that mitochondria were once free-living bacteria with their own division machinery which took up residence within another cell, thus creating the first true eukaryote. The physical fossil record suggests that eukaryotes emerged from prokaryotic ancestors over two billion years ago. Molecular archaeology can help uncover how this occurred. Using a new phylogenetic method with deep time resolution, we have retraced the earliest steps by which the host cell tamed the bacterial endosymbiont.