Thermodynamically allowed phantom cosmology with viscous fluid

In this work, we present an analysis of the phantom zone in a causal viscous cosmology from a thermodynamic point of view. In this description, we consider a chemical potential and the approach of irreversible processes. We assume a flat universe filled with a single dissipative fluid described by a barotropic equation of state, p=ωρ. This model allows us to construct a negative chemical potential for the phantom regime and have positive definite temperature and entropy.