Half-wormholes in nearly AdS$_2$ holography

TL;DR

This paper introduces half-wormhole solutions in nearly AdS$_2$ holography, proposing they restore factorization in the gravitational path integral and relate to averaging over boundary conditions in the dual SYK model.

Contribution

It presents the novel concept of half-wormholes in JT gravity, linking them to boundary condition averaging and providing a gravitational interpretation of factorization restoration.

Findings

Half-wormholes are solutions in JT gravity with spacetime D-branes.

They restore factorization in the gravitational path integral.

The free energy of half-wormholes matches that of a single SYK realization.

Abstract

We find half-wormhole solutions in Jackiw-Teitelboim gravity by allowing the geometry to end on a spacetime D-brane with specific boundary conditions. This theory also contains a Euclidean wormhole which leads to a factorization problem. We propose that half-wormholes provide a gravitational picture for how factorization is restored and show that the Euclidean wormhole emerges from averaging over the boundary conditions. The wormhole is known to be dual to a Sachdev-Ye-Kitaev (SYK) model with random complex couplings. We find that the free energy of the half-wormhole is strikingly similar to that of a single realization of this SYK model. These results suggest that the gravitational path integral computes an average over spacetime D-brane boundary conditions.