3D gravity and non-linear cosmology

TL;DR

This paper explores how adding a non-linear term in scalar curvature R in 3D gravity models can produce accelerated expansion and inflationary behavior, suggesting a geometric origin for dark energy.

Contribution

It introduces a non-linear R term in 3D gravity and demonstrates its potential to generate inflation and late-time acceleration using a van der Waals fluid.

Findings

Non-linear R term can produce inflationary and accelerated expansion phases.

A van der Waals fluid models the matter content and influences cosmic evolution.

Conditions identified where non-linear gravity effects lead to an old accelerated universe.

Abstract

By the inclusion of an additional term, non-linear in the scalar curvature $R$, it is tested if dark energy could rise as a geometrical effect in 3D gravitational formulations. We investigate a cosmological fluid obeying a non-polytropic equation of state (the van der Waals equation) that is used to construct the energy-momentum tensor of the sources, representing the hypothetical inflaton in gravitational interaction with a matter contribution. Following the evolution in time of the scale factor, its acceleration, and the energy densities of constituents it is possible to construct the description of an inflationary 3D universe, followed by a matter dominated era. For later times it is verified that, under certain conditions, the non-linear term in $R$ can generate the old 3D universe in accelerated expansion, where the ordinary matter is represented by the barotropic limit of the van der Waals constituent.