Emergent universe from Energy-Momentum Squared Gravity

In order to bypass the big bang singularity, we develop an emergent universe scenario within a covariant extension of General Relativity known as Energy Momentum Squared Gravity. The extra terms of the model emerge in the high energy regime. Considering dynamics in a Friedmann-Lemaitre-Robertson-Walker background, critical points, representing stable Einstein static states of the phase space, result as solutions. It then turns out that as the equation of state parameter omega gradually declines from a constant value as t -> -infinity, eventually some of the static past eternal solutions find the chance to naturally enter into thermal history through a graceful exit mechanism. In this way, the successful realization of the emergent universe allows an expanding thermal history without the big bang singularity for the spatially flat universe free of cosmological constant. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

To avoid the big bang singularity, a new model of emergent universe is proposed based on the covariant extension of General Relativity known as Energy Momentum Squared Gravity. By considering the dynamics in a specific background and analyzing the solutions, it is shown that some static past eternal solutions can naturally enter the thermal history without encountering the big bang singularity, allowing for an expanding universe history.