• Milestone

Black Holes and Entropy

Jacob D. Bekenstein
Phys. Rev. D 7, 2333 – Published 15 April 1973
An article within the collection: 2015 - General Relativity’s Centennial and the Physical Review D 50th Anniversary Milestones
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Abstract

There are a number of similarities between black-hole physics and thermodynamics. Most striking is the similarity in the behaviors of black-hole area and of entropy: Both quantities tend to increase irreversibly. In this paper we make this similarity the basis of a thermodynamic approach to black-hole physics. After a brief review of the elements of the theory of information, we discuss black-hole physics from the point of view of information theory. We show that it is natural to introduce the concept of black-hole entropy as the measure of information about a black-hole interior which is inaccessible to an exterior observer. Considerations of simplicity and consistency, and dimensional arguments indicate that the black-hole entropy is equal to the ratio of the black-hole area to the square of the Planck length times a dimensionless constant of order unity. A different approach making use of the specific properties of Kerr black holes and of concepts from information theory leads to the same conclusion, and suggests a definite value for the constant. The physical content of the concept of black-hole entropy derives from the following generalized version of the second law: When common entropy goes down a black hole, the common entropy in the black-hole exterior plus the black-hole entropy never decreases. The validity of this version of the second law is supported by an argument from information theory as well as by several examples.

  • Received 2 November 1972

DOI:https://doi.org/10.1103/PhysRevD.7.2333

©1973 American Physical Society

Collections

This article appears in the following collections:

2015 - General Relativity’s Centennial

The editors of the Physical Review journals have curated a collection of landmark papers on General Relativity to celebrate its centennial.

Physical Review D 50th Anniversary Milestones

This collection of seminal papers from PRD highlights research that remains central to developments today in particle physics, quantum field and string theory, gravitation, cosmology, and particle astrophysics.

Authors & Affiliations

Jacob D. Bekenstein*

  • Joseph Henry Laboratories, Princeton University, Princeton, New Jersey 08540
  • Center for Relativity Theory, The University of Texas at Austin, Austin, Texas 78712

  • *National Science Foundation Predoctoral Fellow when this work was initiated.

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Issue

Vol. 7, Iss. 8 — 15 April 1973

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