A covariant entropy conjecture

1999/05/31 by Raphael Bousso · 4 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #astro-ph #gr-qc #hep-th

paper · pdf · doi:10.1088/1126-6708/1999/07/004

published as JHEP 9907:004,1999 · 41 pages, 7 figures. v2,v3: references added

arxiv created 1999/06/24 · openalex publication_date 1999/07/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/29

Abstract

We conjecture the following entropy bound to be valid in all space-times admitted by Einstein's equation: Let A be the area of any two-dimensional surface. Let L be a hypersurface generated by surface-orthogonal null geodesics with non-positive expansion. Let S be the entropy on L. Then S does not exceed A/4. We present evidence that the bound can be saturated, but not exceeded, in cosmological solutions and in the interior of black holes. For systems with limited self-gravity it reduces to Bekenstein's bound. Because the conjecture is manifestly time reversal invariant, its origin cannot be thermodynamic, but must be statistical. Thus it places a fundamental limit on the number of degrees of freedom in nature.

Citations

• Holography and Cosmology
• On particle creation by black holes
• Universal upper bound on the entropy-to-energy ratio for bounded systems
• The four laws of black hole mechanics
• Particle creation by black holes
• Generalized second law of thermodynamics in black-hole physics
• The World as a Hologram
• Black Holes and Entropy

Cited by

• The holographic principle
• Plausible upper limit on the number ofe-foldings
• Self-gravitational corrections to the Cardy–Verlinde formula of the Achúcarro–Ortiz black hole
• Holographic principle [wikipedia]