Gravity Edges Modes and Hayward Term

TL;DR

This paper explores how corner contributions in gravity actions, known as Hayward terms, relate to gravity edge modes and their role in gravitational entropy, connecting holography, AdS/CFT, and string theory perspectives.

Contribution

It demonstrates that Hayward terms encode gravity edge modes responsible for gravitational entropies, providing a unified holographic understanding across different frameworks.

Findings

Hayward term captures gravity edge modes responsible for entropy

Edge modes relate to black hole and holographic entanglement entropy

Edge modes appear in string theory via open strings on horizons

Abstract

We argue that corner contributions in gravity action (Hayward term) capture the essence of gravity edge modes, which lead to gravitational area entropies, such as the black hole entropy and holographic entanglement entropy. We explain how the Hayward term and the corresponding edge modes in gravity are explained by holography from two different viewpoints. One is an extension of AdS/CFT to general spacetimes and the other is the AdS/BCFT formulation. In the final part, we explore how gravity edge modes and its entropy show up in string theory by considering open strings stuck to a Rindler horizon.