We demonstrate 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, φ,X), where R is the Ricci scalar and X = -(∇ φ)2/2 is the kinetic energy of a scalar field φ. In this framework, the horizon entropy S corresponding to equilibrium thermodynamics is proportional to the horizon area A with a constant coefficient, as in the Einstein gravity. We show that for a flat cosmological background with a decreasing Hubble parameter, S globally increases with time.
|出版ステータス||Published - 2009|
|イベント||19th Workshop on General Relativity and Gravitation in Japan, JGRG 2009 - Tokyo, Japan|
継続期間: 2009 11月 30 → 2009 12月 4
|Conference||19th Workshop on General Relativity and Gravitation in Japan, JGRG 2009|
|Period||09/11/30 → 09/12/4|
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