Dynamics of the transitions epochs in cosmological evolution

TL;DR

This paper investigates the transition epochs in cosmological evolution, introducing a new parameter to analyze radiation-to-matter and matter-to-dark energy transitions, and proposes a new dark energy equation of state related to cosmic acceleration.

Contribution

It introduces a novel parameter $$ to study cosmological transitions and formulates a new dark energy equation of state linked to the deceleration parameter.

Findings

Cosmic acceleration requires dark energy EoS $$ in the interval $$ < -2/3.

The new parameter $$ effectively characterizes transition epochs.

Dynamic dark energy must have $$ < -0.47 today for acceleration.

Abstract

We study two transition periods in cosmology: radiation-to-matter and matter-to-dark energy. In each case, we define a new parameter $\chi$ given by the ratios of the two energy densities involved in the transition. Our study of the second epoch is motivated by the need to understand cosmic acceleration. Assuming a dynamic dark energy is the driving force for cosmic acceleration, we formulate a new equation of state for the dark energy given in terms of the ratio $\chi$ and the deceleration parameter, $q$. We have analysed the resultant system of equations, where we vary different parameters and examine the effect on the universe's evolution. For cosmic acceleration to occur, the EoS of the dynamic dark energy must lie in the interval $\omega_{DDE}<-2/3$ at matter-dynamic dark energy equality( equivalently $\omega_{DDE}<-0.47$ today)