Thermodynamics of scalar-tensor gravity
Valerio Faraoni, Andrea Giusti
Abstract
Previously, the Einstein equation has been described as an equation of state, general relativity as the equilibrium state of gravity, and $f(\mathcal{R})$ gravity as a nonequilibrium one. We apply Eckart's first order thermodynamics to the effective dissipative fluid describing scalar-tensor gravity. Surprisingly, we obtain simple expressions for the effective heat flux, ``temperature of gravity'', shear and bulk viscosity, and entropy density, plus a generalized Fourier law in a consistent Eckart thermodynamical picture. Well-defined notions of temperature and approach to equilibrium, missing in the current thermodynamics of spacetime scenarios, naturally emerge.
Topics & Concepts
PhysicsExtended irreversible thermodynamicsDissipative systemNon-equilibrium thermodynamicsVolume viscosityGravitationGeneral relativityThermodynamicsClassical mechanicsEntropy (arrow of time)Equation of stateFirst law of thermodynamicsMathematical physicsViscosityCosmology and Gravitation TheoriesBlack Holes and Theoretical PhysicsAdvanced Thermodynamics and Statistical Mechanics