Online Workshop on Quantum Gravity, Holography and Quantum Information

Gauge/Gravity Duality 2013

As a consequence of electric-magnetic duality, partition functions of four-dimensional gauge theories can be expressed in terms of modular forms in many cases. I will discuss new results for the modularity of topologically twisted partition functions of N=2 and N=4 supersymmetric theories, and in particular how these partititon functions may involve (iterated) integrals of modular forms.

Gauge/Gravity Duality 2013

Gauge/Gravity Duality 2013

The talks will focus on half-BPS boundary conditions for 3d N=2 gauge theories that preserve 2d N=(0,2) supersymmetry. I will review (and extend) the classification of such boundary conditions and the BPS local operators living on them, which form chiral algebras. I define a half-index that counts boundary local operators, or equivalently computes a character of the boundary chiral algebra. With the help of the half-index and some physical intuition, I will identify the action on boundary conditions of some basic dualities, including ``mirror symmetries'' and level-rank dualities. This in turn leads to a definition of duality interfaces. (Work in progress with D. Gaiotto and N. Paquette.)

I will review some recent progress on six-dimensional conformal field theories, highlighting applications to the dynamics of M5-branes. On an orbifold singularity, M5s can fractionate, and they can recombine by sometimes leaving behind a 'frozen' version of the singularity. The CFTs describing these processes also happen to be ubiquitous building blocks for more complicated ones. There is also evidence for other processes where branes recombine in patterns associated to nilpotent orbits of Lie groups, with precise checks obtained by anomalies and moduli space dimensions.

Gauge/Gravity Duality 2013

New perspectives on supersymmetric gauge theories

Gauge/Gravity Duality 2013

Brane Obstructions from the World-Sheet

Gauge/Gravity Duality 2013

Recent developments in holography indicate that the semi-classical Euclidean path-integral of Einstein gravity is much more powerful than previously anticipated. It is capable of reproducing a unitary Page curve for black hole evaporation, and can even capture some features of the discrete nature of black hole microstates. Wormhole geometries play a key role in this context. I will propose a mechanism to explain this in the CFT: the OPE Randomness Hypothesis. This ansatz is a generalization of the Eigenstate Thermalization Hypothesis which applies to chaotic CFTs, and treats OPE coefficients of heavy operators as random variables with a given probability distribution. I will present two applications of this framework: First, it resolves a factorization puzzle in AdS_3/CFT_2 due to the genus-2 wormhole, as raised by Maoz and Maldacena. Second, it provides an argument against global symmetries in quantum gravity.

Non-Relativistic Quantum Gravity

Gauge/Gravity Duality 2013

Gauge/Gravity Duality 2013

New perspectives on supersymmetric gauge theories

Euclidean wormholes comprise exotic types of gravitational solutions, that still challenge our physical intuition and understanding. In the first part of the talk, I will analyse asymptotically AdS wormhole solutions in the context of holography. From a bottom up perspective a study of correlation functions of local and non-local operators indicates the universal properties that any putative holographic dual should exhibit. The system is very weakly cross-coupled in the UV, and becomes strongly cross-coupled in the IR. In the second part, I will describe some concrete field theoretic setups which exhibit such a behaviour and comment on various issues arising in the alpha-parameter interpretation of the wormhole gas.

I will present a new approach to study the RG flow in 3d N=4 gauge theories, based on an analysis of the Coulomb branch of vacua, focusing on U(N) SQCD theories with fundamental matter. The Coulomb branch is described as a complex algebraic variety and important informations about the strongly coupled fixed points of the theory can be extracted from the study of its singularities. I will use this framework to revisit and clarify the classification of infrared fixed points in U(N) SQCD with different amounts of matter hypermultiplets, in particular for the so called ``bad" theories.

I present evidence, both from a GR and a holographic viewpoint, that Coleman's Euclidean axion wormholes do not contribute to the path integral.