  Thermodynamics on the cosmological apparent horizon of a flat
Friedmann-Lemaitre-Robertson-Walker metric has been investigated with
Bekenstein entropy and Hawking temperature on the horizon, and Unruh
temperature for the fluid inside the horizon. This temperature is experienced
by a radial comoving observer infinitesimally close to the horizon due to the
pressure exerted by the fluid bounded by the horizon. An expression for the
entropy of the fluid has been obtained which is found to be proportional to the
volume of the thermodynamic system which implies that the Unruh temperature of
the fluid is inconsistent with the holographic principle. Further, we have been
able to find an expression for the effective entropy of the system. Finally,
assuming a barotropic equation of state $p=w\rho$ ($w$ constant) for the fluid,
it has been shown that the generalized second law holds good for a non-phantom
w, while thermodynamic equilibrium is never possible for such a scenario.
