Talks

I present a consistent theory of classical systems coupled to quantum ones via the path integral formulation. In the classical limit, this is the path integral for stochastic processes like Brownian motion. We apply the formalism to general relativity, since it's reasonable to question whether spacetime should have a quantum nature given its geometric description. In contrast to perturbative quantum gravity, the pure gravity theory is formally renormalisable, and doesn't suffer from negative norm ghosts. This allows for both tabletop experiments and astrophyscical tests of the quantum nature of spacetime.

In this talk I will discuss multi-partite entanglement measures and their computation for holographic theories. I will focus on a particular class of the measures called symmetric measures. If the replica symmetry of the measure is preserved by the bulk solution, then the measure is described by a space with conical singularities whose underlying topology is that of a ball. I will show how such considerations give rise to family multi-partite measures that agree on the holographic state, answering why the holographic states are special.

Characterization of quantum many-body phases through entanglement and non-equilibrium dynamics, such as thermalization, has become a major area of research in recent years. I will discuss calculations of subsystem Renyi entropy in SYK and related models in the large-N limit, mainly based on a new path integral method for computing entanglement entropy of interacting fermions. I will then discuss the non-equilibrium dynamics of SYK models within large-N Schwinger-Keldysh field theory and using finite-N numerics, starting from different types of non-equilibrium initial conditions, like after sudden or slow quenches in the Fermi liquid (FL), non-Fermi liquid (NFL) phases and across NFL-FL transition, as well as starting from a generic pure product state. 

Motivated by SYK model, there have been a lot of activities to understand quantum dynamics in interacting systems via many-body quantum chaos and describe a variety of quantum phases, e.g., heavy Fermi liquids, marginal and non-Fermi liquid, correlated superconductors, etc., through generalizations of the SYK model. I will first discuss some quantum spin glass models related to the SYK model and the characterization of their dynamics through chaos. I will then discuss some lattice and higher-dimensional generalizations of the SYK model to understand higher-dimensional non-Fermi liquids, such as strange metals and other correlated phases.