Modification of black-hole entropy by strings

TL;DR

This paper explores how adding extrinsic curvature terms to string actions affects black-hole entropy and temperature, revealing modifications to the traditional entropy-area relation due to string-gravity coupling.

Contribution

It introduces a generalized string action combining Nambu-Goto and extrinsic curvature terms and analyzes their impact on black-hole thermodynamics.

Findings

Extrinsic curvature opposes Nambu-Goto effects on black-hole temperature

String coupling modifies the entropy-area relation

Conical singularity deficit angle receives contributions from both terms

Abstract

A generalized action for strings which is a sum of the Nambu-Goto and the extrinsic curvature (the energy integral of the surface) terms, is used to couple strings to gravity. It is shown that the conical singularity has deficit angle that has contributions from both the above terms. It is found that the effect of extrinsic curvature is to oppose that of the N-G action for the temperature of the black-hole and to modify the entropy-area relation.