A Proposed Absolute Entropy of Near Extremal Kerr-Newman Black Hole

TL;DR

This paper proposes a new definition of entropy for near extremal Kerr-Newman black holes that aligns with thermodynamic laws, especially the third law, by considering the inner horizon's contribution.

Contribution

It introduces a modified entropy formula for near extremal Kerr-Newman black holes that accounts for the inner horizon and complies with thermodynamic principles.

Findings

Inner horizon has non-zero temperature.

Inner horizon contributes to the total entropy.

Entropy vanishes at absolute zero temperature.

Abstract

Some problems have been found as to the definition of entropy of black hole being applied to the extremal Kerr-Newman case, which has conflicts with the third law of thermodynamics. We have proposed a new modification for the near extremal one, which not only obeys the third law, but also does not conflict with other results in black hole thermodynamics. Then we proved that the inner horizon has temperature and proposed that the inner horizon contributes to the entropy of the near extremal one so that the entropy of it has a modified form and vanishes at absolute zero temperature.