Non-Archimedean character of quantum buoyancy and the generalized second law of thermodynamics

Jacob D. Bekenstein
Phys. Rev. D 60, 124010 – Published 22 November 1999
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Abstract

Quantum buoyancy has been proposed as the mechanism protecting the generalized second law when an entropy-bearing object is slowly lowered towards a black hole and then dropped in. We point out that the original derivation of the buoyant force from a fluid picture of the acceleration radiation is invalid unless the object is almost at the horizon, because otherwise typical wavelengths in the radiation are larger than the object. The buoyant force is here calculated from the diffractive scattering of waves off the object, and found to be weaker than in the original theory. As a consequence, the argument justifying the generalized second law from buoyancy cannot be completed unless the optimal drop point is next to the horizon. The universal bound on entropy is always a sufficient condition for operation of the generalized second law, and can be derived from that law when the optimal drop point is close to the horizon. We also compute the quantum buoyancy of an elementary charged particle; it turns out to be negligible for energetic considerations. Finally, we speculate on the significance of the absence from the bound of any mention of the number of particle species in nature.

  • Received 14 June 1999

DOI:https://doi.org/10.1103/PhysRevD.60.124010

©1999 American Physical Society

Authors & Affiliations

Jacob D. Bekenstein*

  • The Racah Institute of Physics, Hebrew University of Jerusalem, Givat Ram, Jerusalem 91904, Israel

  • *Email address: bekenste@vms.huji.ac.il

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Issue

Vol. 60, Iss. 12 — 15 December 1999

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