What happens at the horizon?

TL;DR

This paper explores the true nature of the black hole horizon, examining whether it is a simple boundary or has complex structure, and connects these ideas to gravity, string theory, and thermodynamics.

Contribution

It proposes mechanisms for horizon structure that challenge traditional no-hair conjectures and links horizon physics to broader theories like string theory and thermodynamics.

Findings

Horizon may have nontrivial structure beyond classical expectations

Connections established between horizon physics, string theory, and thermodynamics

Potential resolutions to Hawking's information paradox

Abstract

The Schwarzschild metric has an apparent singularity at the horizon r=2M. What really happens there? If physics at the horizon is 'normal' laboratory physics, then we run into Hawking's information paradox. If we want nontrivial structure at the horizon, then we need a mechanism to generate this structure that evades the 'no hair' conjectures of the past. Further, if we have such structure, then what would the role of the traditional black hole metric which continues smoothly past the horizon? Recent work has provided an answer to these questions, and in the process revealed a beautiful tie-up between gravity, string theory and thermodynamics.