Viscous Cosmology and Thermodynamics of Apparent Horizon

It is shown that the differential form of Friedmann equations of Friedman-Robertson-Walker (FRW) universe can be recast as a similar form of the first law T(h)dS(h) = dE+WdV of thermodynamics at the apparent horizon of FRW universe filled with the viscous fluid. It is also shown that by employing the general expression of temperature Th = vertical bar kappa vertical bar/2 pi = 1/2 pi(f) over tilde (A) (1 - (r) over tilde (A)/2H (r) over tilde (A)) associated with the apparent horizon of an FRW universe and assumed that the temperature T-m of the energy inside the apparent horizon is proportional to the horizon temperature T-m = bT(h), we are able to show that the generalized second law of thermodynamics holds in the Einstein gravity provided T-h - T-m/(f) over tilde (A) <= (rho + (P) over tilde).