Growth of Cosmic Strings with Field-Dependent Tension

TL;DR

This paper investigates the cosmological growth of cosmic strings with field-dependent tension, demonstrating growth in various backgrounds and identifying conditions for their evolution using dynamical systems analysis.

Contribution

It generalizes previous models by applying dynamical systems techniques to analyze the growth of strings with variable tension in different cosmological backgrounds.

Findings

Growth regions identified in phase space.

Cosmological growth possible in kinating and scaling fixed point backgrounds.

Applicable to both fundamental and effective strings from wrapped branes.

Abstract

A novel mechanism to produce a cosmic network of fundamental superstrings based on a time-varying string tension has been recently proposed. It has been found that fundamental superstrings can grow in a kinating background driven by the rolling of the volume modulus of Type IIB string compactifications towards the minimum of its potential. In this talk, I will generalise this analysis using dynamical systems techniques. First, I will analyse the cosmological growth of strings with a field-dependent tension in a Universe filled with a perfect fluid, finding a growth region in the phase space of this system. This machinery is then applied to both fundamental superstrings and effective strings obtained from wrapping $p$-branes on $(p-1)$- dimensional cycles. I will show how cosmological growth can be achieved in both cases not only in kinating backgrounds, but also in scaling fixed points. This talk is based on arXiv:2502.14953.