Decay of Cosmic String Loops due to Particle Radiation

Abstract

Constraints on the tension and the abundance of cosmic strings depend crucially on the rate at which they decay into particles and gravitational radiation. We study the decay of cosmic string loops in the Abelian-Higgs model by performing field theory simulations of loop formation and evolution. We find that our set of string loops emits particle radiation primarily due to kink collisions, and that the decay time due to these losses is proportional to Lp with p≈2 where L is the loop length. In contrast, the decay time to gravitational radiation scales in proportion to L, and we conclude that particle emission is the primary energy loss mechanism for loops smaller than a critical length scale, while gravitational losses dominate for larger loops.