Y-junction intercommutations of current carrying strings

TL;DR

This paper extends the analysis of cosmic string collisions to current-carrying strings modeled as elastic strings, showing that unlike Nambu-Goto strings, they do not form a third string at Y-junctions under typical conditions.

Contribution

It provides a kinematic analysis of current-carrying string collisions, demonstrating that elastic models do not produce third strings, unlike Nambu-Goto strings, indicating the need for more general models.

Findings

Elastic string models do not form third strings upon collision.

Nambu-Goto strings can form third strings, but elastic models cannot.

Further numerical studies are planned to explore these dynamics.

Abstract

Under certain conditions the collision and intercommutation of two cosmic strings can result in the formation of a third string, with the three strings then remaining connected at Y-junctions. The kinematics and dynamics of collisions of this type have been the subject of analytical and numerical analyses in the special case in which the strings are Nambu-Goto. Cosmic strings, however, may well carry currents, in which case their dynamics is not given by the Nambu-Goto action. Our aim is to extend the kinematic analysis to more general kinds of string model. We focus in particular on the collision of strings described by conservative elastic string models, characteristic of current carrying strings, and which are expected to form in a cosmological context. As opposed to Nambu-Goto strings collisions, we show that in this case the collision cannot lead to the formation of a third elastic string: if dynamically such a string forms then the joining string must be described by a more general equation of state. This process will be studied numerically in a forthcoming publication.