Reconnection of Non-Abelian Cosmic Strings

TL;DR

This paper investigates the reconnection probability of non-abelian cosmic strings, finding it generally remains unity but can vary due to symmetry breaking or quantum effects, with implications for cosmic string interactions.

Contribution

The study provides a detailed analysis of the topology of non-abelian vortex moduli space and how various effects influence string reconnection probabilities.

Findings

Reconnection probability is unity under classical conditions.

Symmetry breaking and quantum effects can reduce reconnection probability.

In U(N) gauge theories, reconnection probability varies from 1/N to 1 depending on energy.

Abstract

Cosmic strings in non-abelian gauge theories naturally gain a spectrum of massless, or light, excitations arising from their embedding in color and flavor space. This opens up the possibility that colliding strings miss each other in the internal space, reducing the probability of reconnection. We study the topology of the non-abelian vortex moduli space to determine the outcome of string collision. Surprisingly we find that the probability of classical reconnection in this system remains unity, with strings passing through each other only for finely tuned initial conditions. We proceed to show how this conclusion can be changed by symmetry breaking effects, or by quantum effects associated to fermionic zero modes, and present examples where the probability of reconnection in a U(N) gauge theory ranges from 1/N for low-energy collisions to one at higher energies.