Cosmological evolution with negative energy densities

TL;DR

This paper explores the effects of negative energy densities on cosmological evolution across various dimensions, providing exact solutions and analyzing conditions for nonsingular dynamics in models with different curvature and cosmological constant values.

Contribution

It offers new exact solutions and a comprehensive analysis of cosmological models with negative energy densities, extending understanding beyond traditional positive-energy scenarios.

Findings

Exact solutions for flat models with negative energy densities.

Conditions for nonsingular cosmological evolution.

Impact of negative energy densities on hyperbolic vacuum polarization.

Abstract

For general number of spatial dimensions we investigate the cosmological dynamics driven by a cosmological constant and by a source with barotropic equation of state. It is assumed that for both those sources the energy density can be either positive or negative. Exact solutions of the cosmological equations are provided for flat models. For models with curved space and with zero cosmological constant the general solutions are expressed in terms of the hypergeometric function. The qualitative evolution is described for all values of the equation of state parameter. We specify the values of that parameter and the combinations of the signs for the cosmological constant and matter energy density for which the cosmological dynamics is nonsingular. An example is considered with positive cosmological constant and negative matter energy density induced by the polarization of the hyperbolic vacuum.