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 ThdSh = 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 associated with the apparent horizon of an FRW universe and assumed that the temperature Tm of the energy inside the apparent horizon is proportional to the horizon temperature Tm= bTh, we are able to show that the generalized second law of thermodynamics holds in the Einstein gravity provided Th-Tm/r~A ≤(ρ+P~).
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 ThdSh = 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 associated with the apparent horizon of an FRW universe and assumed that the temperature Tm of the energy inside the apparent horizon is proportional to the horizon temperature Tm= bTh, we are able to show that the generalized second law of thermodynamics holds in the Einstein gravity provided Th-Tm/r~A ≤(ρ+P~).
M. Akbar. Viscous Cosmology and Thermodynamics of Apparent Horizon[J]. 中国物理快报, 2008, 25(12): 4199-4202.
M. Akbar. Viscous Cosmology and Thermodynamics of Apparent Horizon. Chin. Phys. Lett., 2008, 25(12): 4199-4202.
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associated with the apparent horizon of an FRW universe and assumed that the temperature Tm of the energy inside the apparent horizon is proportional to the horizon temperature Tm= bTh, we are able to show that the generalized second law of thermodynamics holds in the Einstein gravity provided Th-Tm/r~A ≤(ρ+P~).