JT Gravity from Partial Reduction and Defect Extremal Surface

TL;DR

This paper constructs a three-dimensional bulk dual for JT gravity coupled with a CFT bath using partial reduction, incorporating a defect brane with fluctuations, and confirms the agreement of entropy calculations from different methods.

Contribution

It introduces a novel higher-dimensional dual for JT gravity with a defect brane, enabling new approaches to black hole information and gravity/ensemble duality.

Findings

The defect brane has small transverse fluctuations modeled as a dilaton.

The island formula and defect extremal surface yield matching entropy results.

Provides a Lorentzian higher-dimensional dual framework for JT gravity.

Abstract

We propose the three-dimensional bulk dual for Jackiw-Teitelboim gravity coupled with CFT$_2$ bath based on partial reduction. The bulk dual is classical AdS gravity with a defect brane which has small fluctuation in transverse direction. We derive full Jackiw-Teitelboim gravity action by considering the transverse fluctuation as a dilaton field. We demonstrate that the fine grained entropy computed from island formula precisely agrees with that computed from defect extremal surface. Our construction provides a Lorentzian higher dimensional dual for Jackiw-Teitelboim gravity and therefore offers a framework to study problems such as black hole information paradox as well as gravity/ensemble duality.