Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10723517 | Physics Letters B | 2010 | 9 Pages |
Abstract
We show that it is possible to obtain a picture of equilibrium thermodynamics on the apparent horizon in the expanding cosmological background for a wide class of modified gravity theories with the Lagrangian density f(R,Ï,X), where R is the Ricci scalar and X is the kinetic energy of a scalar field Ï. This comes from a suitable definition of an energy-momentum tensor of the “dark” component that respects to a local energy conservation in the Jordan frame. In this framework the horizon entropy S corresponding to equilibrium thermodynamics is equal to a quarter of the horizon area A in units of gravitational constant G, as in Einstein gravity. For a flat cosmological background with a decreasing Hubble parameter, S globally increases with time, as it happens for viable f(R) inflation and dark energy models. We also show that the equilibrium description in terms of the horizon entropy S is convenient because it takes into account the contribution of both the horizon entropy SË in non-equilibrium thermodynamics and an entropy production term.
Related Topics
Physical Sciences and Engineering
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Authors
Kazuharu Bamba, Chao-Qiang Geng, Shinji Tsujikawa,