Thermodynamic Constraints on the Dark Sector

In this paper, we present a unified scheme based on the fluid description of the dark sector of the universe. The scheme captures models with interaction between dark energy and dark matter, being the core of generalization the time-varying equation-of-state parameter $ω(a)$ and the time-dependent interactions through the interaction function $ε(a)$, where $a$ is the scale factor. Furthermore, we propose thermodynamics constraints on this generalized class of models using the laws of thermodynamics which are combined with observational data. In order to test the observational viability of the unified model, we perform a Bayesian analysis using cosmic chronometers, type Ia supernovae, cosmic microwave background, and angular baryon acoustic oscillation measurements.