Lovelock type gravity and small black holes in heterotic string theory

TL;DR

This paper demonstrates that a modified Lovelock gravity action accurately reproduces the entropy of small heterotic string black holes across all dimensions, extending previous results and linking near-horizon geometry with string microstates.

Contribution

It introduces a Lovelock type effective action that yields exact black hole entropy matching string theory predictions in any dimension.

Findings

Black hole entropy matches 4π√nw for all dimensions.

A unique parameter choice makes the entropy independent of D.

The action applies to AdS2×S^{D-2} near horizon geometries.

Abstract

We analyze near horizon behavior of small D-dimensional 2-charge black holes by modifying tree level effective action of heterotic string with all extended Gauss-Bonnet densities. We show that there is a nontrivial and unique choice of parameters, independent of D, for which the black hole entropy in any dimension is given by 4\pi\sqrt{nw}, which is exactly the statistical entropy of 1/2-BPS states of heterotic string compactified on T^{9-D}\times S^1 with momentum n and winding w. This extends the results of Sen [JHEP 0507 (2005) 073] to all dimensions. We also show that our Lovelock type action belongs to the more general class of actions sharing the simmilar behaviour on the AdS_2\times S^{D-2} near horizon geometry.