Gravitational Radiation and the Small-Scale Structure of Cosmic Strings

TL;DR

This paper calculates gravitational radiation from cosmic strings with small amplitude waves, revealing that highly asymmetric wave trains emit negligible radiation, which could impact cosmological phenomena like cosmic rays and gravitational waves.

Contribution

It extends previous calculations to cases with vastly different wavelengths of wave-trains on cosmic strings, showing that radiation emission can be exponentially suppressed in such regimes.

Findings

Power radiated vanishes exponentially for highly asymmetric wave-trains.

Small excitations in one direction can be long-lived, affecting string network scales.

Potential implications for ultra-high energy cosmic rays and gravitational wave signals.

Abstract

We calculate the gravitational radiation emitted by an infinite cosmic string with two oppositely moving wave-trains, in the small amplitude approximation. After comparing our result to the previously studied cases we extend the results to a new regime where the wavelengths of the opposing wave-trains are very different. We show that in this case the amount of power radiated vanishes exponentially. This means that small excitations moving in only one direction may be very long lived, and so the size of the smallest scales in a string network might be much smaller than what one would expect from gravitational back reaction. This result allows for a potential host of interesting cosmological possibilities involving ultra-high energy cosmic rays, gamma ray bursts and gravitational wave bursts.