Strings in de Sitter space

TL;DR

This paper investigates global and local strings in de Sitter space by solving the full coupled equations, revealing closed solutions with supermassive string characteristics and regular configurations when the string core is within the horizon.

Contribution

It provides the first comprehensive analysis of coupled equations for strings in de Sitter space, including solutions with regular cores inside the horizon.

Findings

Solutions resemble supermassive strings with horizon singularities

Global strings can be regular if their core is inside the horizon

Only closed solutions are found for the coupled equations

Abstract

We study both global as well as local (Nielsen-Olesen) strings in de Sitter space. While these type of topological defects have been studied in the background of a de Sitter metric previously, we study here the full set of coupled equations. We find only ``closed'' solutions. The behaviour of the metric tensor of these solutions resembles that of ``supermassive'' strings with a curvature singularity at the cosmological horizon. For global strings (and the composite defect) we are able to construct solutions which are regular on the interval from the origin to the cosmological horizon if the global string core lies completely inside the horizon.