Jackiw-Teitelboim Gravity from Holonomies: Discrete BF Formulation and Boundary Symmetries

TL;DR

This paper presents a non-perturbative, discrete BF formulation of 2D JT gravity, revealing boundary symmetries and deriving black hole entropy directly from holonomy data without relying on the Schwarzian action.

Contribution

It introduces a fully discrete, boundary-focused BF framework for JT gravity, analyzing boundary conditions, symmetries, and entropy in a novel lattice setting.

Findings

Boundary symmetries include affine Kac-Moody and Virasoro algebras.

Black hole entropy is derived from holonomy data and dilaton Casimir.

The discrete model reproduces Bekenstein-Hawking entropy without Schwarzian action.

Abstract

We develop a fully discrete and non-perturbative formulation of two-dimensional Jackiw-Teitelboim (JT) gravity within the BF framework. Using group-valued holonomies and Lie-algebra--valued dilatons, the bulk theory is shown to be purely topological, with all physical information encoded at the boundary. We analyze admissible discrete boundary conditions and derive the corresponding asymptotic symmetry algebras directly at the lattice level, including an affine Kac-Moody symmetry and its Brown-Henneaux reduction to a Virasoro algebra, together with the associated Virasoro-dilaton structure. A precise operator product expansion (OPE) dictionary is established by taking the controlled continuum limit of the discrete Poisson brackets. Beyond asymptotic symmetries, we provide an effective boundary description and a representation-theoretic quantization organized by monodromy sectors. Within this discrete framework, black hole entropy follows from gauge-invariant holonomy data and is expressed in terms of the dilaton Casimir, reproducing the Bekenstein--Hawking result without invoking a fundamental Schwarzian action.