Bremsstrahlung in the gravitational field of a cosmic string

TL;DR

This paper analyzes bremsstrahlung radiation emitted by an electron passing near a cosmic string, revealing how the conical space geometry enables radiation processes forbidden in flat spacetime.

Contribution

It provides the first detailed calculation of bremsstrahlung in the gravitational field of a cosmic string within QED, including analytic expressions for different energy regimes.

Findings

Cross section and electromagnetic energy emitted are computed.

Results differ from flat spacetime predictions due to conical geometry.

Comparison with scalar QED and classical electrodynamics shows unique effects of cosmic string.

Abstract

In the framework of QED we investigate the bremsstrahlung process for an electron passing by a straight static cosmic string. This process is precluded in empty Minkowski space-time by energy and momentum conservation laws. It happens in the presence of the cosmic string as a consequence of the conical structure of space, in spite of the flatness of the metric. The cross section and emitted electromagnetic energy are computed and analytic expressions are found for different energies of the incoming electron. The energy interval is divided in three parts depending on whether the energy is just above electron rest mass $M$, much larger than $M$, or exceeds $M/\delta$, with $\delta$ the string mass per unit length in Planck units. We compare our results with those of scalar QED and classical electrodynamics and also with conic pair production process computed earlier.