Cosmic Strings Collision in Cosmological Backgrounds

TL;DR

This paper investigates the dynamics of cosmic string collisions and junction formations within expanding cosmological backgrounds, analyzing how loop size relative to the Hubble rate influences these processes through analytical and numerical methods.

Contribution

It provides a comprehensive analysis of cosmic string loop collisions and junction formation dynamics across different loop size regimes in expanding universes, combining analytical and numerical approaches.

Findings

Junction formation depends on loop size relative to the Hubble rate.

Large super-horizon loops exhibit different collision dynamics than small sub-horizon loops.

The study characterizes the zipping and unzipping processes during string collisions.

Abstract

The collisions of cosmic strings loops and the dynamics of junctions formations in expanding backgrounds are studied. The key parameter controlling the dynamics of junctions formation, the cosmic strings zipping and unzipping is the relative size of the loops compared to the Hubble expansion rate at the time of collision. We study analytically and numerically these processes for large super-horizon size loops, for small sub-horizon size loops as well as for loops with the radii comparable to the Hubble expansion rate at the time of collision.