Thermodynamics in<i>f</i>(<i>R</i>) gravity in the Palatini formalism

Abstract

We investigate thermodynamics of the apparent horizon in $f(R)$ gravity in\nthe Palatini formalism with non-equilibrium and equilibrium descriptions. We\ndemonstrate that it is more transparent to understand the horizon entropy in\nthe equilibrium framework than that in the non-equilibrium one. Furthermore, we\nshow that the second law of thermodynamics can be explicitly verified in both\nphantom and non-phantom phases for the same temperature of the universe outside\nand inside the apparent horizon.\n