THERMODYNAMICS OF VISCOUS DARK ENERGY IN AN RSII BRANEWORLD

We show that for an RSII braneworld filled with interacting viscous dark energy and dark matter, one can always rewrite the Friedmann equation in the form of the first law of thermodynamics, dE = T(h)dS(h) + WdV, at the apparent horizon. In addition, the generalized second law of thermodynamics can be fulfilled in a region enclosed by the apparent horizon on the brane for both constant and time-variable five-dimensional Newton's constant G(5). These results hold regardless of the specific form of the dark energy. Our study further supports the belief that in an accelerating universe with spatial curvature, the apparent horizon is a physical boundary from the thermodynamical point of view.