Article,
Thermodynamical Aspects of Gravity: New insights
(2009)cite arxiv:0911.5004 Comment: 85 pages; 5 figures; Invited Review to appear in Reports on Progress in Physics.
Abstract
The fact that one can associate thermodynamic properties with horizons brings
together principles of quantum theory, gravitation and thermodynamics and
possibly offers a window to the nature of quantum geometry. This review
discusses certain aspects of this topic concentrating on new insights gained
from some recent work. After a brief introduction of the overall perspective,
Sections 2 and 3 provide the pedagogical background on the geometrical features
of bifurcation horizons, path integral derivation of horizon temperature, black
hole evaporation, structure of Lanczos-Lovelock models, the concept of Noether
charge and its relation to horizon entropy. Section 4 discusses several
conceptual issues introduced by the existence of temperature and entropy of the
horizons. In Section 5 we take up the connection between horizon thermodynamics
and gravitational dynamics and describe several peculiar features which have no
simple interpretation in the conventional approach. The next two sections
describe the recent progress achieved in an alternative perspective of gravity.
In Section 6 we provide a thermodynamic interpretation of the field equations
of gravity in any diffeomorphism invariant theory and in Section 7 we obtain
the field equations of gravity from an entropy maximization principle. The last
section provides a summary.
