Cosmological Models in Energy-Momentum-Squared Gravity

TL;DR

This paper explores the impact of higher-order energy-momentum tensor terms on cosmological models, revealing exact solutions and their implications for universe evolution, singularities, and accelerated expansion.

Contribution

It introduces a novel class of cosmological theories incorporating higher-order matter terms, extending beyond traditional curvature-based modifications.

Findings

Derived exact solutions for isotropic universes.

Analyzed early and late-time cosmological behaviors.

Identified conditions for singularity avoidance and accelerated expansion.

Abstract

We study the cosmological effects of adding terms of higher-order in the usual energy-momentum tensor to the matter lagrangian of general relativity. This is in contrast to most studies of higher-order gravity which focus on generalising the Einstein-Hilbert curvature contribution to the lagrangian. The resulting cosmological theories include many particular theories, like bulk viscous cosmologies, loop quantum gravity, K-essence, and brane-world cosmologies. We find a range of exact solutions for isotropic universes, discuss their behaviours with reference to the early and late-time evolution, accelerated expansion, and the occurrence or avoidance of singularities. We briefly discuss extensions to anisotropic cosmologies and delineate the situations where the higher-order matter terms will dominate over anisotropies on approach to cosmological singularities.