Dynamical Origin of the Entropy of a Black Hole

Abstract

Modes of physical fields which are located inside a horizon and which cannot be observed by a distant observer are identified with dynamical degrees of freedom of a black hole. A new invariant statistical mechanical definition of a black-hole's entropy is proposed. It is shown that the main contribution to the entropy is given by thermally excited `invisible' modes propagating in the close vicinity of the horizon. A calculation based on the proposed definition yields a value of the entropy which is in good agreement with the usually adopted value.

14 pages, LaTeX, report NORDITA 93/45A (July 1993) (revision of the paper (submitted earlier to Phys.Rev.D) in response to referee's comments). NO CHANGES, the corrupted old LaTeX file of the paper was repaired