LAUSR

Thermodynamics on the horizon of a flat universe at late times is studied in holographic cosmological models that assume an associated entropy on the horizon. In such models, a $\mathrm{\ensuremath{\Lambda}}(t)$ model similar to a time-varying $\mathrm{\ensuremath{\Lambda}}(t)$ cosmology is favored because of the consistency of energy flows across the horizon. Based on this consistency, a $\mathrm{\ensuremath{\Lambda}}(t)$ model with a power-law term proportional to ${H}^{\ensuremath{\alpha}}$ is formulated to systematically examine the evolution of the Bekenstein-Hawking entropy. Here, $H$ is the Hubble parameter and $\ensuremath{\alpha}$ is a free parameter whose value is a real number. The present model always satisfies the second law of thermodynamics on the horizon. In particular, the universe for $\ensuremath{\alpha}l2$ tends to approach thermodynamic equilibriumlike states. Consequently, when $\ensuremath{\alpha}l2$, the maximization of the entropy should be satisfied as well, at least in the last stage of the evolution of an expanding universe. A relaxationlike process before the last stage is also examined from a thermodynamics viewpoint.