Revisiting the Logarithmic Corrections to the Black Hole Entropy

TL;DR

The paper reevaluates logarithmic corrections to extremal and near-extremal black hole entropy by treating extremal zero-modes exactly through a near-extremal regulator, which yields Schwarzian (or super-Schwarzian) effective dynamics. It shows that these zero-modes drive temperature-dependent log corrections and induce distinct degeneracy structures for non-supersymmetric versus supersymmetric black holes, with SUSY cases matching microscopic index computations. The authors derive the full one-loop determinant around the near-extremal background, obtaining a scaling Z1-loop ∼ Q^{c_log}(Q^3T)^{3/2} and entropy corrections S = πQ^2 + 4π^2Q^3T + c_log log Q + (3/2) log(Q^3T), and discuss the regime of validity. In SUSY theories, the zero-mode sector aligns with an N = 4 JT gravity framework, yielding an index that reproduces degeneracies, while non-SUSY cases can have vanishing extremal degeneracies, tying the gravitational path integral to microscopic counting and localization in BPS sectors.

Abstract

Logarithmic corrections to the entropy of extremal black holes have been successfully used to accurately match degeneracies from microscopic constructions to calculations of the gravitational path integral. In this paper, we revisit the problem of deriving such corrections for the case of extremal black holes, either non-supersymmetric or supersymmetric, and for near-extremal black holes. The zero-modes that are present at extremality are crucial, since their path integral cannot be treated quadratically and needs to be regulated. We show how the regulated result can be obtained by taking the zero-temperature limit of either the $4d$ Einstein-Maxwell or $4d$ supergravity path integral to find the Schwarzian or super-Schwarzian theories. This leads to drastically different estimates for the degeneracy of non-supersymmetric and supersymmetric extremal black holes. In a companion paper, we discuss how such zero-modes affect the calculation of BPS black holes degeneracies, using supersymmetric localization for an exact computation of the gravitational path integral.