Talks

This course will introduce some advanced topics in general relativity related to describing gravity in the strong field and dynamical regime. Topics covered include properties of spinning black holes, black hole thermodynamics and energy extraction, how to define horizons in a dynamical setting, formulations of the Einstein equations as constraint and evolution equations, and gravitational waves and how they are sourced.

Topics will include (but are not limited to): - Quantum error correction in quantum gravity and condensed matter - Quantum information scrambling and black hole information - Physics of random tensor networks and random unitary circuits

 

Unlike conventional global symmetries that act on all of space, subsystem symmetries act only on rigid subspaces such as lines, planes or fractal regions. Such symmetries are of interest for their close connection to fracton physics and in their own right. In this talk, I discuss phenomena that can occur in two-dimensional systems with subsystem symmetry and anyon excitations, where the symmetry fractionalizes on anyon excitations. This turns out to be manifest in the mobility of the fractionalized excitations under dynamics that respect the symmetry. Such symmetry fractionalization was previously thought to be impossible, and indeed there are a number of differences from conventional symmetry fractionalization. I will present a general framework to describe subsystem symmetry fractionalization in two dimensions, and give a number of simple examples of this phenomenon in commuting Pauli Hamiltonians.

This talk is based on arXiv:2203.13244, work in collaboration with David Stephen, Arpit Dua, José Garre-Rubio and Dominic Williamson.

Zoom Link: https://pitp.zoom.us/j/93741883840?pwd=RlMrUGwwVEt5WFdoNGpkMmdSVXp5UT09

I review a recent approach to connecting quantum gravity and the real world by deconstantizing the constants of nature, and using their conjugate as a time variable. This is nothing but a generalization of unimodular gravity. The wave functions are then packets of plane waves moving in a space that generalizes the Chern-Simons functional. For appropriate states they link up with classical cosmology in the appropriate limit. There are however deviations, namely during the matter to Lambda transition, raising the possibility that quantum gravity could be in action here and now. At the other extreme I show how this approach can be used to resolve the cosmological singularity, and perhaps more.

Zoom Link: https://pitp.zoom.us/j/94010122575?pwd=L291eHNSOG1wZmpCL1lmWHVJaEwwdz09

This course is designed to introduce modern machine learning techniques for studying classical and quantum many-body problems encountered in condensed matter, quantum information, and related fields of physics. Lectures will focus on introducing machine learning algorithms and discussing how they can be applied to solve problem in statistical physics. Tutorials and homework assignments will concentrate on developing programming skills to study the problems presented in lecture.

Topics will include (but are not limited to): Canonical formulation of constrained systems, The Dirac program, First order formalism of gravity, Loop Quantum Gravity, Spinfoam models, Research at PI and other approaches to quantum gravity.

Topics will include (but are not limited to): Canonical formulation of constrained systems, The Dirac program, First order formalism of gravity, Loop Quantum Gravity, Spinfoam models, Research at PI and other approaches to quantum gravity.

This course will introduce some advanced topics in general relativity related to describing gravity in the strong field and dynamical regime. Topics covered include properties of spinning black holes, black hole thermodynamics and energy extraction, how to define horizons in a dynamical setting, formulations of the Einstein equations as constraint and evolution equations, and gravitational waves and how they are sourced.

In this talk, I intend to give a pedagogical, nonetheless biased, introduction to String Cosmology. After briefly reviewing the Lambda-CDM model and motivating inflation, we will remind ourselves that early universe cosmology remains singular and waiting for alternatives. That will be our cue to consider string theory to define our gravity sector and string thermodynamics to define our matter sector. We will learn how that doesn't work unless we consider more string corrections (in fact, an infinity of them!). Once we are stringy enough, we will be able to build a full cosmological model that is non-singular and already poses itself as an alternative to inflation at the background level.

Zoom Link: https://pitp.zoom.us/j/98491655811?pwd=ZzArNjFVMmZIdE1STjd2TVNWSlZtZz09

Population studies of gravitational-wave events allow us to probe stellar evolution and formation mechanisms of compact binaries. Recent work has painted a conflicting portrait of the distribution of black hole spins in merging binaries. In this talk, I describe the emerging picture of black hole spin using observations from LIGO-Virgo–KAGRA with a new spin model. We find evidence for two subpopulations of binary black holes: 1) merging binaries containing black holes with negligible spin, 2) binaries preferentially aligned with the orbital angular momentum and rapidly spinning. These results are consistent with predictions from studies of angular momentum transport in stars and suggest that the subpopulation of spinning black holes may be spun up via tidal interactions. I will also share insights of the binary black hole population using the latest catalogue of gravitational-wave events.

Zoom Link: https://pitp.zoom.us/j/93713298741?pwd=eFo2Q1lSTVBESWcyZXJlcFVKZ2hRQT09

This course is designed to introduce modern machine learning techniques for studying classical and quantum many-body problems encountered in condensed matter, quantum information, and related fields of physics. Lectures will focus on introducing machine learning algorithms and discussing how they can be applied to solve problem in statistical physics. Tutorials and homework assignments will concentrate on developing programming skills to study the problems presented in lecture.