Article Title

Gravitational statistical mechanics: A model

Type of Work

Article

Date

2001

Journal Title

Classical and Quantum Gravity

Journal ISSN

0264-9381

Journal Volume

18

Journal Issue

23

First Page

5125

Last Page

5142

DOI

10.1088/0264-9381/18/23/309

Abstract

Using the quantum Hamiltonian for a gravitational system with boundary, we find the partition function and derive the resulting thermodynamics. The Hamiltonian is the boundary term required by functional differentiability of the action for the Lorentzian general relativity. In this model, states of quantum geometry are represented by spin networks. We show that the statistical mechanics of the model reduces to that of a simple non-interacting gas of particles with spin. Using both canonical and grand canonical descriptions, we investigate two temperature regimes determined by the fundamental constant in the theory, m. In the high temperature limit (kT m), the model is thermodynamically stable. For low temperatures (kT m) and for macroscopic areas of the bounding surface, the entropy is proportional to the area (with logarithmic correction), providing a simple derivation of the Bekenstein–Hawking result. By comparing our results to known semiclassical relations we are able to fix the fundamental scale m. Also in the low temperature, macroscopic limit, the quantum geometry on the boundary forms a 'condensate' in the lowest energy level (j = 1/2).

Hamilton Areas of Study

Physics