Gravitational entropy of a Kerr black hole

Abstract

The gravitational entropy of a Kerr black hole is calculated using a classical estimator based on the Bel-Robinson tensor, which has been recently proposed by Clifton, Ellis, and Tavakol. We prove that, in the frame we consider, Clifton et al.’s estimator does not reproduce the Bekenstein-Hawking entropy of a Kerr black hole.