Comments on the black hole information problem

TL;DR

This paper discusses how nonlocal effects in string theory can resolve the black hole information paradox by allowing information retrieval without violating causality or the equivalence principle.

Contribution

It proposes that unitarity is restored through suppressed nonlocal effects, providing a framework consistent with effective field theory and black hole complementarity.

Findings

Nonlocal effects are exponentially suppressed by the Bekenstein-Hawking entropy.

Effective field theory remains valid for certain time-slicings.

Information can be retrieved without causality violations or conflicting with the equivalence principle.

Abstract

String theory provides numerous examples of duality between gravitational theories and unitary gauge theories. To resolve the black hole information paradox in this setting, it is necessary to better understand how unitarity is implemented on the gravity side. We argue that unitarity is restored by nonlocal effects whose initial magnitude is suppressed by the exponential of the Bekenstein-Hawking entropy. Time-slicings for which effective field theory is valid are obtained by demanding the mutual back-reaction of quanta be small. The resulting bounds imply that nonlocal effects do not lead to observable violations of causality or conflict with the equivalence principle for infalling observers, yet implement information retrieval for observers who stay outside the black hole.