New edge modes and corner charges for first-order symmetries of 4D gravity

TL;DR

This paper introduces a new set of noncommuting symmetries and edge modes in 4D gravity, providing a framework that resembles a Poincare group with structure functions, and is suitable for discretization and quantum gravity applications.

Contribution

It presents novel noncommuting frame-translation symmetries in 4D gravity that express diffeomorphisms as composite transformations, with implications for discretization and quantum gravity.

Findings

Symmetries resemble a Poincare group with structure functions.

Edge modes and charges are more amenable to discretization.

Sketches a strategy for charge algebra in quantum gravity.

Abstract

We present a set of noncommuting frame-translation symmetries in 4D gravity in tetrad-connection variables, which allow expressing diffeomorphisms as composite transformations. Working on the phase space level for finite regions, we pay close attention to the corner piece of the generators, discuss various possible charge brackets, relative definitions of the charges, coupling to spinors and relations to other charges. What emerges is a picture of the symmetries and edge modes of gravity that bears local resemblance to a Poincare group $SO(1,3)\ltimes \mathbb{R}^{1,3}$, but possesses structure functions. In particular, we argue that the symmetries and charges presented here are more amenable to discretisation, and sketch a strategy for this charge algebra, geared toward quantum gravity applications.