Regular Bouncing Cosmological Solutions in Effective Actions in Four Dimensions

TL;DR

This paper explores cosmological models derived from effective four-dimensional actions linked to string and supergravity theories, identifying conditions for regular bouncing solutions and highlighting the role of additional sectors like Ramond-Ramond fields.

Contribution

It provides a detailed analysis of bouncing solutions in effective actions with specific parameters, revealing how string theory sectors influence regularity of cosmological bounces.

Findings

Bouncing solutions are achievable under certain parameter conditions.

Inclusion of Ramond-Ramond sectors ensures regularity in string effective actions.

Multiple solution types, including Friedmann-like, are identified.

Abstract

We study cosmological scenarios resulting from effective actions in four dimensions which are, under some assumptions, connected with multidimensional, supergravity and string theories. These effective actions are labeled by the parameters $\omega$, the dilaton coupling constant, and $n$ which establishes the coupling between the dilaton and a scalar field originated from the gauge field existing in the original theories. There is a large class of bouncing as well as Friedmann-like solutions. We investigate under which conditions bouncing regular solutions can be obtained. In the case of the string effective action, regularity is obtained through the inclusion of contributions from the Ramond-Ramond sector of superstring.