Cyclical Behaviour in Early Universe Cosmologies

TL;DR

This paper investigates early universe cosmologies modeled by scalar-tensor theories, revealing complex dynamical behaviors like heteroclinic cycles and bouncing cosmologies, which may suggest chaotic evolution and connect to string theory models.

Contribution

It introduces a new dynamical systems framework for early universe cosmologies with no asymptotic equilibrium states, highlighting cyclical and bouncing behaviors with potential chaos.

Findings

Existence of heteroclinic cycles in cosmological dynamics

Presence of bouncing and cyclical behaviors in early universe models

Potential connection to string theory effective actions

Abstract

We study early universe cosmologies derived from a scalar-tensor action containing cosmological constant terms and massless fields. The governing equations can be written as a dynamical system which contains no past or future asymptotic equilibrium states (i.e. no sources nor sinks). This leads to dynamics with very interesting mathematical behaviour such as the existence of heteroclinic cycles. The corresponding cosmologies have novel characteristics, including cyclical and bouncing behaviour possibly indicating chaos. We discuss the connection between these early universe cosmologies and those derived from the low-energy string effective action.