Cosmology in presence of dark energy in an emergent gravity scenario

TL;DR

This paper derives modified Friedmann equations within an emergent gravity framework incorporating dark energy, showing that standard cosmological behaviors can be explained with dark energy present from the universe's early stages.

Contribution

It introduces analogues of Friedmann equations in emergent gravity with dark energy, linking dark energy density to cosmological parameters and early universe behavior.

Findings

Deceleration parameter exceeds 0.5 in matter domination.

Deceleration parameter exceeds 1 in radiation domination.

Deceleration parameter drops below -1 in dark energy scenario.

Abstract

We obtain the analogues of the Friedman equations in an emergent gravity scenario in the presence of dark energy. The background metric is taken to be Friedman-Lemaitre-Robertson-Walker (FLRW). We show that if $\dot\phi ^{2}$ is the dark energy density (in units of the critical density) then (a) for total energy density greater than the pressure (non-relativistic scenario, matter domination) the deceleration parameter $q(t)\approx\frac {1}{2} [1 + 27 \dot\phi ^{2}+...] > \frac{1}{2}$ (b) for total energy density equal to 3 times the pressure (relativistic case, radiation domination), the deceleration parameter $q(t)\approx 1 + 18\dot\phi ^{2} +... > 1$ and (c) for total energy density equal to the negative of the pressure (dark energy scenario), the deceleration parameter $q(t)< -1$. Our results indicate that many aspects of standard cosmology can be accommodated with the presence of dark energy right from the beginning of the universe where the time parameter $t\equiv \frac{t}{t_{0}}$, $t_{0}$ being the present epoch.