Swing surfaces and holographic entanglement beyond AdS/CFT

TL;DR

This paper introduces a new holographic entanglement entropy method for non-AdS holographic models, using swing surfaces composed of null and spacelike geodesics, applicable to flat and warped AdS spacetimes.

Contribution

It proposes a novel swing surface prescription for holographic entanglement entropy beyond AdS/CFT, supported by an extension of the Lewkowycz-Maldacena argument.

Findings

The swing surface prescription reproduces known results in non-AdS holography.

Supports the first law of entanglement entropy in these models.

Extends the holographic entanglement entropy framework to flat and warped AdS spacetimes.

Abstract

We propose a holographic entanglement entropy prescription for general states and regions in two models of holography beyond AdS/CFT known as flat$_3$/BMSFT and (W)AdS$_3$/WCFT. Flat$_3$/BMSFT is a candidate of holography for asymptotically flat three-dimensional spacetimes, while (W)AdS$_3$/WCFT is relevant in the study of black holes in the real world. In particular, the boundary theories are examples of quantum field theories that feature an infinite dimensional symmetry group but break Lorentz invariance. Our holographic entanglement entropy proposal is given by the area of a swing surface that consists of ropes, which are null geodesics emanating from the entangling surface at the boundary, and a bench, which is a spacelike geodesic connecting the ropes. The proposal is supported by an extension of the Lewkowycz-Maldacena argument, reproduces previous results based on the Rindler method, and satisfies the first law of entanglement entropy.