Entropy and thermodynamics of ghost dark energy

We study the thermodynamics of the ghost model of dark energy in a flat Friedmann-Robertson-Walker (FRW) universe enveloped by a Hubble horizon. We show that the Friedmann equation of the FRW universe, in the presence of ghost dark energy, can be transformed to the first law of thermodynamics on the Hubble horizon. Using this procedure, we extract the entropy expression associated with the horizon in this model. We find that the area relation for the entropy expression is modified and an additional term that is proportional to the volume of the system, A(3/2), appears in the entropy relation. We also find that for late time, where the temperature of the Universe scales as the temperature of its horizon, T = bT(in), the generalized second law of thermodynamics can be secured provided 1/2 <= b <= 1, where T and T-in are the horizon and the matter fields' temperatures, respectively.