Geodesic motion in the space-time of cosmic strings interacting via magnetic fields

TL;DR

This paper investigates how test particles move around interacting cosmic strings modeled by Abelian-Higgs fields, revealing bound orbits and potential observational signatures like gravitational waves.

Contribution

It introduces a BPS-limit model of interacting p-q-strings and analyzes test particle geodesics numerically, highlighting new bound orbit phenomena due to string interactions.

Findings

Interaction leads to bound orbits absent in non-interacting models

Numerical solutions classify geodesics by energy, angular momentum, and momentum along the string

Potential implications for detecting cosmic strings via gravitational wave signals

Abstract

We study the geodesic motion of test particles in the space-time of two Abelian-Higgs strings interacting via their magnetic fields. These bound states of cosmic strings constitute a field theoretical realization of p-q-strings which are predicted by inflationary models rooted in String Theory, e.g. brane inflation. In contrast to previously studied models describing p-q-strings our model possesses a Bogomolnyi-Prasad-Sommerfield (BPS) limit. If cosmic strings exist it would be exciting to detect them by direct observation. We propose that this can be done by the observation of test particle motion in the space-time of these objects. In order to be able to make predictions we have to solve the field equations describing the configuration as well as the geodesic equation numerically. The geodesics can then be classified according to the test particle's energy, angular momentum and momentum along the string axis. We find that the interaction of two Abelian-Higgs strings can lead to the existence of bound orbits that would be absent without the interaction. We also discuss the minimal and maximal radius of orbits and comment on possible applications in the context of gravitational wave emission.