High resolution calibration of string network evolution

TL;DR

This paper calibrates the velocity-dependent one-scale model for cosmic string evolution using extensive high-resolution simulations, analyzing numerical choices' effects on key parameters and observational constraints.

Contribution

It provides the most comprehensive calibration of the VOS model to date, accounting for numerical sensitivities and their impact on cosmic string observational predictions.

Findings

Numerical choices significantly affect the loop chopping parameter.

Calibration results are robust across various cosmological expansion rates.

Implications for observational constraints on cosmic strings are discussed.

Abstract

The canonical velocity-dependent one-scale (VOS) model for cosmic string evolution contains a number of free parameters which cannot be obtained ab initio. Therefore it must be calibrated using high resolution numerical simulations. We exploit our state of the art graphically accelerated implementation of the evolution of local Abelian-Higgs string networks to provide a statistically robust calibration of this model. In order to do so, we will make use of the largest set of high resolution simulations carried out to date, for a variety of cosmological expansion rates, and explore the impact of key numerical choices on model calibration, including the dynamic range, lattice spacing, and the choice of numerical estimators for the mean string velocity. This sensitivity exploration shows that certain numerical choices will indeed have consequences for observationally crucial parameters, such as the loop chopping parameter. To conclude, we will also briefly illustrate how our results impact observational constraints on cosmic strings.