An Effective Field Theory for Binary Cosmic Strings

TL;DR

This paper develops an effective field theory framework for modeling gravitational radiation from binary systems of cosmic strings, accounting for their extended structure and wiggles, and explores the renormalization of string tension.

Contribution

It extends the EFT formalism to include extended objects like cosmic strings with wiggles, introducing new perturbative parameters and power counting rules.

Findings

Derived an effective action for gravitational radiation from cosmic strings.

Identified the role of string bending modes in generating gravitational waves.

Analyzed ultraviolet divergences and obtained the renormalization group flow of string tension.

Abstract

We extend the effective field theory (EFT) formalism for gravitational radiation from a binary system of compact objects to the case of extended objects. In particular, we study the EFT for a binary system consisting of two infinitely-long cosmic strings with small velocity and small spatial substructure, or "wiggles". The complexity of the system requires the introduction of two perturbative expansion parameters, constructed from the velocity and size of the wiggles, in contrast with the point particle case, for which a single parameter is sufficient. This further requires us to assign new power counting rules in the system. We integrate out the modes corresponding to potential gravitons, yielding an effective action for the radiation gravitons. We show that this action describes a changing quadrupole, sourced by the bending modes of the string, which in turn generates gravitational waves. We study the ultraviolet divergences in this description, and use them to obtain the classical renormalization group flow of the string tension in such a setting.