Entropy of Kerr-Newman Black Hole Continuously Goes to Zero when the Hole Changes from Nonextreme Case to Extreme Case

Abstract

A new formulation of the Bekenstein-Smarr formula of a Kerr-Newman black hole is given. The re-defined black hole entropy continuously goes to zero as the black hole temperature approaches absolute zero, which satisfies the Nernst theorem. Our new result suggests that the Kerr-Newman black hole should be regarded as a composite thermodynamic system composed of two sub-systems, its outer horizon and its inner horizon. There exists a new quantum thermal effect, "Hawking absorption", near the inner horizon of the black hole.