Toward stringy horizons

TL;DR

This paper introduces a new framework for describing causal structures and horizons in holographic systems using string theory concepts, highlighting differences from classical black hole models and exploring quantum chaotic behavior.

Contribution

It develops a stringy language for causal structure and horizons, incorporating boundary operator algebras and a stringy causal depth parameter, advancing the understanding of holographic dualities beyond Einstein gravity.

Findings

Emergent sharp horizons above Hawking--Page temperature in large N limit of N=4 SYM

Stringy horizons differ from toy models of black hole information loss

Methods can probe violations of the equivalence principle and stringy nonlocality

Abstract

We take a first step towards developing a new language to describe causal structure, event horizons, and quantum extremal surfaces (QES) for the bulk description of holographic systems beyond the standard Einstein gravity regime. By considering the structure of boundary operator algebras, we introduce a stringy ``causal depth parameter'', which quantifies the depth of the emergent radial direction in the bulk, and a certain notion of ergodicity on the boundary. We define stringy event horizons in terms of the half-sided inclusion property, which is related to a stronger notion of boundary ergodic or quantum chaotic behavior. Using our definition, we argue that above the Hawking--Page temperature, there is an emergent sharp horizon structure in the large $N$ limit of $\mathcal{N}=4$ Super-Yang--Mills at finite nonzero 't Hooft coupling. In contrast, some previously considered toy models of black hole information loss do not have a stringy horizon. Our methods can also be used to probe violations of the equivalence principle for the bulk gravitational system, and to explore aspects of stringy nonlocality.