Oct 3 – 7, 2022
Perimeter Institute for Theoretical Physics
America/Toronto timezone

Gong Show Talks and Abstracts

Ankit Aggarwal, University of Amsterdam

Ward Identities for near horizon symmetries

We derive the ward identities for the near horizon symmetries of Schwarzschild blackhole as found by Donnay, Giribet, Gonzalez, and Pino in 2016. We further show that these ward identities imply an "emergent" soft graviton theorem near the horizon. Moreover, we derive this soft theorem from by studying scattering near the horizon of the Schwarzschild blackhole. Based on an upcoming work with Nava Gaddam.

Monireh Ahmadpour, University of Tehran

Entanglement Entropy in Presence of TT-bar deformation

A recent proposal relates a deformed field theory with TT operator to the gravity theory on the AdS background which has finite radial cutoff. In our paper we calculated entanglement measures like holographic entanglement entropy and mutual information when deformed field theory had finite temperature and we investigated qualitatively the behavior of these quantities for different temperature and cutoff limits. In my talk, I will briefly present some of our interesting results.

Giovanni Canepa, Centre de Physique Théorique

Corner Structure of 4d General Relativity using the BFV formalism

In This talk I will describe a local Poisson structure (up to homotopy) associated to corners in four-dimensional gravity in the coframe (Palatini--Cartan) formalism. This is achieved through the use of the BFV formalism.

Roukaya Dekhil, Ludwig Maximilian University of Munich

Entanglement in superpositions of spin networks states with different graph structures

The proposal that spacetime and its geometric properties are emergent entities from purely non-geometric degrees of freedom that are subsequently closely related to entanglement measures has attracted a lot of attention in the sector of quantum information (QI). We present a straightforward implementation of these techniques in quantum gravity (QG) models where we focus on a particular set of QG states . More concretely, we show how studying the entanglement properties of a superposition of QG states, precisely spin network graph states endowed with different combinatorial structures, naturally leads to a generalization of the usual von Neumann entropy obtained for spin network states in LQG calculations. This is indeed achieved once we borrow different entropic notions and measures from quantum information theory, where in the studied case of the superposition of states, the von Neumann entropy of entangled regions gives rise to the so called interaction entropy in QI already at the kinematical level of the theory. Moreover, a comparison between the second quantization formalism of this scheme based on the superposition of states and that of LQG results is presented.

Arnaud Delfante, University of Mons

Holographic Lorentz and Carroll Frames

It has been shown that the solution space of three-dimensional gravity contains an additional free function if we relax the Bondi gauge. This additional function allows to promote the boundary metric to a Lorentz or Carroll frame, in asymptotically AdS or flat spacetimes. In this talk, we focus on the symplectic structure of this solution space, which is finite and obtained taking advantage of the built-in ambiguities. Remarkably, there is a prescription of the selected corner term that makes smooth the flat limit of the AdS symplectic structure. This prescription reveals a holographic anomaly in the boundary Lorentz symmetry, that rotates the frame, and which survives in the flat limit, thus predicting the existence of quantum anomalies in conformal Carrollian field theories.

Florian Ecker, Technische Universität Wien

dS$_2$ as excitation of AdS$_2$

I introduce a family of 2D dilaton gravity models with state-dependent constant curvature so that dS2 emerges as an excitation of AdS2. Curiously, the strong coupling region corresponds to the asymptotic region geometrically. Apart from these key differences, many features resemble the Almheiri--Polchinski model. I discuss perturbative and non-perturbative thermodynamical stability, bubble nucleation through matter shockwaves, and semiclassical backreaction effects. In some of these models, we find that low temperatures are dominated by AdS2 but high temperatures are dominated by dS2, concurrent with a recent proposal by Susskind.

Gloria Odak, Centre de Physique Théorique

Brown-York charges for null boundaries with different boundary conditions

We show how the improved Noether charge prescription on null hypersurfaces gives different results with different choices of boundary Lagrangians corresponding to admissible covariant phase space polarization. None of the choices considered, however, eliminates the discrepancy with the null Brown-York charge already pointed out in the literature for the case of Dirichlet boundary lagrangian. As a side result, we show a choice of polarization which requires no boundary lagrangian for the variational principle, and which may be relevant for the literature on complexity.