Thermodynamics of viscous dark energy in an RSII braneworld

TL;DR

This paper demonstrates that in an RSII braneworld with viscous dark energy and dark matter, the Friedmann equation can be expressed as the first law of thermodynamics at the apparent horizon, supporting the thermodynamic interpretation of cosmic acceleration.

Contribution

It shows the thermodynamic equivalence of the Friedmann equation in RSII braneworlds with viscous dark energy, including variable G_5, regardless of dark energy form.

Findings

First law of thermodynamics holds at apparent horizon.

Generalized second law is valid for variable G_5.

Results support thermodynamic interpretation of accelerating universe.

Abstract

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, $dE=T_hdS_h+WdV$, at apparent horizon. In addition, the generalized second law of thermodynamics can fulfilled in a region enclosed by the apparent horizon on the brane for both constant and time variable 5-dynamical Newton's constant $G_5$. These results hold regardless of the specific form of the dark energy. Our study further support that in an accelerating universe with spatial curvature, the apparent horizon is a physical boundary from the thermodynamical point of view.