Universe consisting of diffusive dark fluids: thermodynamics and stability analysis

Thermodynamics of diffusive DM/DE systems

We discuss the energy density,temperature and entropy of dark matter (DM) and dark energy (DE) as functions of the scale factor $a$ in an expanding universe. In a model of non-interacting dark components we repeat a derivation from thermodynamics of the well-known relations between the energy density,entropy and temperature. In particular, the entropy is constant as a consequence of the energy conservation. We consider a model of the DM/DE interaction where DM energy density increase is proportional to the particle density. In such a model the dependence of the energy density and the temperatu…

Does diffusion mechanism favor the emergent scenario of the universe?

In the present work, the flat FLRW Universe has been modelled with cosmic matter in the form of diffusive barotropic fluid. The diffusive fluid undergoes dissipation due to diffusion mechanism in the form of cosmological scalar field. From the perspective of non-equilibrium thermodynamics, the evolution equations of the universe have been formulated. By a suitable choice of the cosmological scalar field, emergent scenario of the universe has been obtained.

标量-张量引力的框架不变扩散表述

Frame invariant diffusive formulation of scalar-tensor gravity

本文探讨了标量-张量引力的框架不变扩散表述，指出传统温度定义不具框架不变性，提出通过框架不变的有效流体来解释广义相对论与扩散平衡的关系。