Reconnection of Colliding Cosmic Strings

TL;DR

This paper analytically studies the reconnection process of cosmic strings, showing classical inevitability for vortex strings and probabilistic nature for D-strings, aligning with previous numerical and quantum results.

Contribution

It provides a unified analytical framework for understanding reconnection in both vortex and D-strings, highlighting the classical versus quantum differences.

Findings

Reconnection is classically inevitable for vortex strings at small velocities.

D-string reconnection probability is quantum mechanical, matching nonperturbative results.

Analytical results agree with previous numerical and quantum calculations.

Abstract

For vortex strings in the Abelian Higgs model and D-strings in superstring theory, both of which can be regarded as cosmic strings, we give analytical study of reconnection (recombination, inter-commutation) when they collide, by using effective field theories on the strings. First, for the vortex strings, via a string sigma model, we verify analytically that the reconnection is classically inevitable for small collision velocity and small relative angle. Evolution of the shape of the reconnected strings provides an upper bound on the collision velocity in order for the reconnection to occur. These analytical results are in agreement with previous numerical results. On the other hand, reconnection of the D-strings is not classical but probabilistic. We show that a quantum calculation of the reconnection probability using a D-string action reproduces the nonperturbative nature of the worldsheet results by Jackson, Jones and Polchinski. The difference on the reconnection -- classically inevitable for the vortex strings while quantum mechanical for the D-strings -- is suggested to originate from the difference between the effective field theories on the strings.