A transition between bouncing hyper-inflation to {\Lambda}CDM from diffusive scalar fields

TL;DR

This paper explores a unified dark energy-dark matter model based on Two Measures Theories, showing a transition from bouncing hyper-inflation to the standard b5b4CDM model, with the deviation controlled by a diffusion constant.

Contribution

It introduces a diffusive non-conservative stress-energy tensor within a unified dark sector model, extending Two Measures Theories to describe early universe bounce and late-time b5b4CDM behavior.

Findings

Model exhibits a bounce and hyper-inflation in early universe for certain diffusion constants.

Late universe evolution converges to b5b4CDM as a stable fixed point.

Deviation from b5b4CDM is governed by the diffusion constant C_2.

Abstract

We consider the history of the universe from a possible big bang or a bounce into a late period of a unified interacting dark energy - dark matter model. The model is based on the Two Measures Theories (T.M.T.) which introduces a metric independent volume element and this allows us to construct a unification of dark energy and dark matter. A generalization of the T.M.T. gives a diffusive non-conservative stress energy momentum tensor in addition to the conserved stress energy tensor which appear in Einstein equations. These leads to a formulation of interacting DE-DM dust models in the form of a diffusive type interacting Unified Dark Energy and Dark Matter scenario. The deviation from $\Lambda$CDM is determined by the diffusion constant $C_2$. For $C_2=0$ the model is indistinguishable from $\Lambda$CDM. Numerical solutions of the theories show that in some $C_2 \neq 0$ the evolution of the early universe is governed by Stiff equation of state or the universe bounces to hyper inflation. But all of those solutions have a final transition to $\Lambda$CDM as a stable fixed point for the late universe.