# Type I Abelian Higgs strings: evolution and Cosmic Microwave Background constraints

## TL;DR

This paper presents the first simulations of Type I Abelian Higgs cosmic string networks across matter and radiation eras, analyzing their evolution and constraints from Cosmic Microwave Background data, with implications for high-energy physics models.

## Contribution

It introduces comprehensive simulations of Type I Abelian Higgs strings including CMB constraints, revealing their compatibility with high-energy scales and low self-couplings.

## Key findings

- String separation is independent of $eta$
- Energy-momentum correlators scale with string tension
- Low self-coupling strings can satisfy CMB bounds at GUT scales

## Abstract

We present results from the first simulations of networks of Type I Abelian Higgs cosmic strings to include both matter and radiation eras and Cosmic Microwave Background (CMB) constraints. In Type I strings, the string tension is a slowly decreasing function of the ratio of the scalar and gauge mass-squared, $\beta$. We find that the mean string separation shows no dependence on $\beta$, and that the energy-momentum tensor correlators decrease approximately in proportion to the square of the string tension, with additional O(1) correction factors which asymptote to constants below $\beta \lesssim 0.01$. Strings in models with low self-couplings can therefore satisfy current CMB bounds at higher symmetry-breaking scales. This is particularly relevant for models where the gauge symmetry is broken in a supersymmetric flat direction, for which the effective self-coupling can be extremely small. If our results can be extrapolated to $\beta \simeq 10^{-15}$, even strings formed at $10^{16}$ GeV (approximately the grand unification scale in supersymmetric extensions of the Standard Model) can be compatible with CMB constraints.