Scaling of cosmic string loops

TL;DR

This paper investigates the evolution of cosmic string loops, revealing a scaling regime with larger loops than previously thought, which tightens cosmological bounds on string tension.

Contribution

It demonstrates that cosmic string loops reach a true scaling regime with larger characteristic sizes, contrasting earlier simulations that found smaller loops.

Findings

Loops scale as 0.1 times the cosmic time

Tighter nucleosynthesis bounds on string tension Gμ

Large loops have significant cosmological implications

Abstract

We study the spectrum of loops as a part of a complete network of cosmic strings in flat spacetime. After a long transient regime, characterized by production of small loops at the scale of the initial conditions, it appears that a true scaling regime takes over. In this final regime the characteristic length of loops scales as $0.1 t$, in contrast to earlier simulations which found tiny loops. We expect the expanding-universe behavior to be qualitatively similar. The large loop sizes have important cosmological implications. In particular, the nucleosynthesis bound becomes $G\mu \lesssim 10^{-7}$, much tighter than before.