The effect of kinematic constraints on multi-tension string network evolution

TL;DR

This paper investigates how kinematic constraints influence the evolution and scaling behavior of multi-tension string networks with junctions in an expanding universe, extending understanding of cosmic superstring dynamics.

Contribution

It introduces explicit kinematic constraints into the evolution equations, revealing their role in enabling scaling solutions in complex string networks with junctions.

Findings

Kinematic constraints enable scaling in regimes previously thought non-scaling.

Predicted scaling densities for networks with cosmic superstring interactions.

Extended the parameter space where string networks can achieve scaling.

Abstract

We consider the evolution of a network of strings in an expanding universe, allowing for the formation of junctions between strings of different tensions. By explicitly including, in the velocity-dependent evolution equations for the network, kinematic constraints associated with the formation of Y-shaped string junctions, we show how they lead to scaling solutions in regimes where they would not otherwise be found, thereby extending the range of parameters which lead to scaling. By incorporating these constraints we are able to study their general behaviour for networks with cosmic superstring interaction rules, and predict the scaling densities expected by these networks.