Instanton effects in string cosmology

TL;DR

This paper explores how gauge dyonic string solutions in heterotic string theory influence cosmological models, showing that non-trivial Yang-Mills backgrounds can avoid singularities at the big bang.

Contribution

It introduces a cosmological model based on gauge dyonic string solutions with Green-Schwarz and Chern-Simons corrections, highlighting singularity avoidance with non-trivial Yang-Mills backgrounds.

Findings

Non-trivial Yang-Mills backgrounds lead to non-singular cosmological solutions.

Trivial backgrounds result in fields becoming singular at the big bang.

The model incorporates world sheet and string loop corrections.

Abstract

We consider the gauge dyonic string solution of the K3 compactified heterotic string theory in a four dimensional cosmological context. Since for this solution Green-Schwarz as well as Chern-Simons corrections have been taken into account it contains both world sheet and string loop corrections. The cosmological picture is obtained by rotating the world volume of the gauge dyonic string into two space like dimensions and compactifying those dimensions on a two torus. We compare the result with gauge neutral extreme and non-extreme cosmologies and find that the non-trivial Yang Mills background leads to a solution without any singularities whereas for trivial Yang-Mills backgrounds some of the fields become always singular at the big bang.