Entropy and Quantum Gravity
 Citation data:

Entropy, ISSN: 10994300, Vol: 17, Issue: 12, Page: 81748186
 Publication Year:
 2015
 Repository URL:
 http://philsciarchive.pitt.edu/id/eprint/12297
 DOI:
 10.3390/e17127873
 Author(s):
 Publisher(s):
 Tags:
 Physics and Astronomy
article description
We give a review, in the style of an essay, of the author's 1998 mattergravity entanglement hypothesis which, unlike the standard approach to entropy based on coarsegraining, offers a definition for the entropy of a closed system as a real and objective quantity. We explain how this approach offers an explanation for the Second Law of Thermodynamics in general and a nonparadoxical understanding of information loss during black hole formation and evaporation in particular. It also involves a radically different from usual description of black hole equilibrium states in which the total state of a black hole in a box together with its atmosphere is a pure stateentangled in just such a way that the reduced state of the black hole and of its atmosphere are each separately approximately thermal. We also briefly recall some recent work of the author which involves a reworking of the stringtheory understanding of black hole entropy consistent with this alternative description of black hole equilibrium states and point out that this is free from some unsatisfactory features of the usual string theory understanding. We also recall the author's recent arguments based on this alternative description which suggest that the Anti de Sitter space (AdS)/conformal field theory (CFT) correspondence is a bijection between the boundary CFT and just the matter degrees of freedom of the bulk theory.