Interactions between several types of cosmic strings

TL;DR

This paper investigates the interactions among various types of cosmic strings, revealing complex phase structures and conditions favoring bound state formation, with implications for cosmic string network evolution.

Contribution

It provides a detailed analysis of interactions between different cosmic string types, including new insights into the energetics and phase structure of bosonic superconducting strings.

Findings

Scalar fields enhance attraction between strings.

Bound states are energetically favored in certain conditions.

Bosonic superconducting strings exhibit richer phase structures.

Abstract

We study the interaction of several types of static straight cosmic strings, including local strings, global strings, and bosonic superconducting strings with and without magnetic currents. First, we evaluate the interaction energy of two widely separated cosmic strings using the point source formalism and show that the most dominant contribution to the interaction energy comes from the excitation of the lightest mediator particles in a underlying theory. The interaction energy at arbitrary separation distances is then analyzed numerically by the gradient flow method. It turns out that an additional scalar field introduced in the bosonic superconducting string becomes an additional source of attraction. For such a bosonic superconducting string, we find that a string with two winding numbers is energetically favorable compared to two strings with a single winding number in a certain parameter region. Our analysis reveals that a phase structure of bosonic superconducting strings is richer than that of local and global strings and that the formation of bound states at intersections of bosonic superconducting strings is favored.