Generalized Second Law of Thermodynamics in Extended Theories of Gravity

By employing the general expression for temperature T-h = vertical bar kappa vertical bar/2 pi = 1/2 pi(r) over tilde (A) (1-((r) over tilde) over dot(A)/2H (r) over tilde (A)) associated with the apparent horizon of FRW universe and assuming a region of an expanding universe enclosed by the apparent horizon as a thermal system in equilibrium, we are able to show that the generalized second law of thermodynamics holds in Gauss-Bonnet and more general Lovelock gravities.