A thermodynamic model for dark energy including particle creation or destruction processes

Abstract

Thermodynamic analyses of dark energy as a relativistic fluid indicates that this intriguing component of the universe mimics a bulk viscous pressure when the parameter of its barotropic equation of state varies with time. Since in cosmology bulk viscosity and creation or destruction of matter are closely linked processes, we propose in this work a brief thermodynamic study of dark energy considering that particles can be created or destroyed in the fluid. We derive new expressions for quantities such as particle density, entropy density etc. that have been shown to be sensitive to this new ingredient. We also obtain new thermodynamic constraints and compare them with those where the number of particles is conserved. In particular, we found that in the presence of a sink, dark energy tends towards the cosmological constant over time regardless of the sign of its chemical potential and without violating the laws of thermodynamics.