Dynamics of domain wall networks with junctions

TL;DR

This study combines analytic methods and large-scale 3D simulations to investigate the evolution of domain wall networks with junctions, providing evidence for their approach to scaling and updating cosmological bounds on their energy scale.

Contribution

It introduces a comprehensive analysis of domain wall networks with junctions across various models and cosmological epochs, supporting the no-frustration conjecture with extensive simulations.

Findings

Evidence for a gradual approach to scaling in domain wall networks

Updated cosmological bound on defect energy scale below 10 keV

Comparison of different junction types and their impact on network dynamics

Abstract

We use a combination of analytic tools and an extensive set of the largest and most accurate three-dimensional field theory numerical simulations to study the dynamics of domain wall networks with junctions. We build upon our previous work and consider a class of models which, in the limit of large number $N$ of coupled scalar fields, approaches the so-called `ideal' model (in terms of its potential to lead to network frustration). We consider values of $N$ between N=2 and N=20, and a range of cosmological epochs, and we also compare this class of models with other toy models used in the past. In all cases we find compelling evidence for a gradual approach to scaling, strongly supporting our no-frustration conjecture. We also discuss the various possible types of junctions (including cases where there is a hierarchy of them) and their roles in the dynamics of the network. Finally, we revise the Zel'dovich bound and provide an updated cosmological bound on the energy scale of this type of defect network: it must be lower than $10 {\rm keV}$.