Reversible and irreversible spacetime thermodynamics for general Brans-Dicke theories
- SISSA, Via Bonomea 265, 34136 Trieste (Italy)
We derive the equations of motion for Palatini F(R) gravity by applying an entropy balance law TdS={delta}Q+{delta}N to the local Rindler wedge that can be constructed at each point of spacetime. Unlike previous results for metric F(R), there is no bulk viscosity term in the irreversible flux {delta}N. Both theories are equivalent to particular cases of Brans-Dicke scalar-tensor gravity. We show that the thermodynamical approach can be used ab initio also for this class of gravitational theories and it is able to provide both the metric and scalar equations of motion. In this case, the presence of an additional scalar degree of freedom and the requirement for it to be dynamical naturally imply a separate contribution from the scalar field to the heat flux {delta}Q. Therefore, the gravitational flux previously associated to a bulk viscosity term in metric F(R) turns out to be actually part of the reversible thermodynamics. Hence we conjecture that only the shear viscosity associated with Hartle-Hawking dissipation should be associated with irreversible thermodynamics.
- OSTI ID:
- 21503970
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 83, Issue 2; Other Information: DOI: 10.1103/PhysRevD.83.024032; (c) 2011 American Institute of Physics; ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
Similar Records
Spherically symmetric thin shells in Brans-Dicke theory of gravity
Nonequilibrium thermodynamics of spacetime: The role of gravitational dissipation
Related Subjects
GENERAL PHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
BALANCES
BRANES
DEGREES OF FREEDOM
ENTROPY
EQUATIONS OF MOTION
GRAVITATION
HEAT FLUX
METRICS
SCALAR FIELDS
SPACE-TIME
THERMODYNAMICS
VISCOSITY
DIFFERENTIAL EQUATIONS
EQUATIONS
MEASURING INSTRUMENTS
PARTIAL DIFFERENTIAL EQUATIONS
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES
WEIGHT INDICATORS