Generalised velocity-dependent one-scale model for current-carrying strings

TL;DR

This paper extends the velocity-dependent one-scale model to include arbitrary currents on superconducting cosmic strings, enabling more accurate predictions of their evolution and potential observational signatures.

Contribution

The authors develop a generalized VOS model that incorporates arbitrary currents and charges, broadening the scope of cosmic string network evolution analysis.

Findings

Reproduces known models for wiggly and chiral strings

Provides a framework for studying superconducting string evolution

Enables exploration of observational signatures of current-carrying strings

Abstract

We develop an analytic model to quantitatively describe the evolution of superconducting cosmic string networks. Specifically, we extend the velocity-dependent one-scale (VOS) model to incorporate arbitrary currents and charges on cosmic string worldsheets under two main assumptions, the validity of which we also discuss. We derive equations that describe the string network evolution in terms of four macroscopic parameters: the mean string separation (or alternatively the string correlation length) and the root mean square (RMS) velocity which are the cornerstones of the VOS model, together with parameters describing the averaged timelike and spacelike current contributions. We show that our extended description reproduces the particular cases of wiggly and chiral cosmic strings, previously studied in the literature. This VOS model enables investigation of the evolution and possible observational signatures of superconducting cosmic string networks for more general equations of state, and these opportunities will be exploited in a companion paper.