Black Hole Entropy and String Instantons

TL;DR

This paper explores how string theory modifies black hole entropy and temperature, suggesting non-local quantum effects could help recover information from black holes.

Contribution

It introduces a string instanton mechanism that alters the entropy-area relation and affects black hole thermodynamics beyond classical predictions.

Findings

Entropy is reduced by a factor involving string tension

Black hole temperature exceeds the Hawking value in this model

Quantum effects cause horizon materialization

Abstract

The coupling of a string to gravity allows for Schwarzschild black holes whose entropy to area relation is $S=(A/4)(1-4\mu)$, where $\mu$ is the string tension. This departure from the A/4 universality results from a string instanton generating a black hole with smaller entropy at a temperature exceeding the Hawking value. The temperature is sensitive to the presence of classical matter outside the black hole horizon but the entropy is not. The horizon materializes at the quantum level. It is conjectured that such a macroscopic non local effect may be operative in retrieving information from incipient black holes.