Qualitative Analysis of Early Universe Cosmologies

TL;DR

This paper qualitatively analyzes how a cosmological constant influences the dynamics of homogeneous cosmologies derived from string theory, revealing oscillatory behaviors and analytical solutions in phase space.

Contribution

It introduces a qualitative framework for understanding the effects of a cosmological constant in string-derived cosmologies, highlighting oscillatory dynamics and equilibrium solutions.

Findings

Existence of oscillating cosmological models with expanding and contracting phases.

Identification of heteroclinic cycles influencing dynamics.

Analytical solutions at equilibrium points.

Abstract

A qualitative analysis is presented for a class of homogeneous cosmologies derived from the string effective action when a cosmological constant is present in the matter sector of the theory. Such a term has significant effects on the qualitative dynamics. For example, models exist which undergo a series of oscillations between expanding and contracting phases due to the existence of a heteroclinic cycle in the phase space. Particular analytical solutions corresponding to the equilibrium points are also found.