Light from Cosmic Strings

TL;DR

This paper investigates how cosmic strings can emit light through a gravitational effect, producing a distinctive flat spectrum of photon radiation that could serve as an observable signature for detecting cosmic strings.

Contribution

It introduces the concept of gravitational Aharonov-Bohm effect causing photon emission from cosmic strings and evaluates the radiation from various string features like cusps and kinks.

Findings

Photon emission has a flat spectrum up to the string scale.

Cusps emit a focused beam of photons.

Kinks emit photons along a curve, and kink-kink collisions emit isotropically.

Abstract

The time-dependent metric of a cosmic string leads to an effective interaction between the string and photons - the "gravitational Aharonov-Bohm" effect -- and causes cosmic strings to emit light. We evaluate the radiation of pairs of photons from cosmic strings and find that the emission from cusps, kinks and kink-kink collisions occurs with a flat spectrum at all frequencies up to the string scale. Further, cusps emit a beam of photons, kinks emit along a curve, and the emission at a kink-kink collision is in all directions. The emission of light from cosmic strings could provide an important new observational signature of cosmic strings that is within reach of current experiments for a range of string tensions.