Zipping and Unzipping in String Networks: Dynamics of Y-junctions

TL;DR

This paper investigates the stability and dynamics of Y-shaped string junctions in cosmic string networks, analyzing conditions for zipping and unzipping, and exploring implications for realistic string interaction models.

Contribution

It provides a detailed analysis of the stability and evolution of Y-junctions under tension balance, including conditions for zipping and unzipping in string networks.

Findings

Y-junctions are stable under tension deformations.

The angle at the junction relaxes to equilibrium and grows relativistically.

Decelerated zipping and unzipping solutions are identified.

Abstract

We study, within the Nambu-Goto approximation, the stability of massive string junctions under the influence of the tensions of three strings joining together in a Y-type configuration. The relative angle $\beta$ between the strings at the junction is in general time-dependent and its evolution can lead to zipping or unzipping of the three-string configuration. We find that these configurations are stable under deformations of the tension balance condition at the junction. The angle $\beta$ relaxes at its equilibrium value and the junction grows relativistically. We then discuss other potential "unzipping agents" including monopole/string forces for long strings and curvature for loops, and we investigate specific solutions exhibiting decelerated zipping and unzipping of the Y-junction. These results provide motivation for incorporating the effects of realistic string interactions in network evolution models with string junctions.