Eigenbranes in Jackiw-Teitelboim gravity

TL;DR

The paper addresses the tension between boundary discreteness and bulk quasi-normal decay in JT gravity by recasting JT as matrix ensembles and introducing eigenbranes—fixed-energy boundaries corresponding to fixed eigenvalues.It develops and compares three JT definitions (disks, genus expansion, and eigenbranes) to isolate IR discreteness, and shows that fixing N eigenvalues yields a gravity theory that captures discrete spectral features and late-time erratic oscillations characteristic of finite quantum systems.Using genus expansion, exact brane methods, and conditional densities, the authors demonstrate how delta spikes and voids arise, how erratic plateaus emerge in the local spectral form factor, and how geometric disconnection underpins the coarse-grained/discrete dual descriptions.The work suggests a gravitational interpretation of discrete spectra via eigenbranes, outlines extensions to JT supergravity, and raises prospects for bulk observables built from brane insertions and boundary mergers.

Abstract

It was proven recently that JT gravity can be defined as an ensemble of L x L Hermitian matrices. We point out that the eigenvalues of the matrix correspond in JT gravity to FZZT-type boundaries on which spacetimes can end. We then investigate an ensemble of matrices with 1<<N<<L eigenvalues held fixed. This corresponds to a version of JT gravity which includes N FZZT type boundaries in the path integral contour and which is found to emulate a discrete quantum chaotic system. In particular this version of JT gravity can capture the behavior of finite-volume holographic correlators at late times, including erratic oscillations.