Piercing of domain walls: new mechanism of gravitational radiation

TL;DR

This paper introduces a novel mechanism called piercing gravitational radiation (PGR), where particles perforate domain walls, excite branon waves, and generate gravitational waves, especially prominent with relativistic particles or photons.

Contribution

It derives the spectral-angular distribution of PGR in a simplified weak gravity model, revealing new insights into gravitational wave generation from domain wall perforation.

Findings

PGR amplitude is enhanced for relativistic particles or photons.

The spectral-angular distribution exhibits infrared, ultraviolet, and collinear divergences.

Different cut-off schemes are discussed for various dimensions.

Abstract

Domain wall (DW) moving in media undergoes the friction force due to particle scattering. However certain particles are not scattered, but perforate the wall. As a result, the wall gets excited in the form of the branon wave, while the particle experiences an acceleration jump. This gives rise to generation of gravitational waves which we call "piercing gravitational radiation" (PGR). Though this effect is of higher order in the gravitational constant than the quadrupole radiation from the collapsing DWs, its amplitude is enhanced in the case of relativistic particles or photons because of absence of the velocity factor which is present in the quadrupole formula. We derive the spectral-angular distribution of PGR within the simplified model of the weakly gravitating particle-wall system in Minkowski space-time of arbitrary dimensions. Within this model the radiation amplitude is obtained analytically. The spectral-angular distribution of PGR in such an approach suffers from infrared and ultraviolet divergences as well as from collinear divergence in the case of a massless perforating particle. Different cut-off schemes appropriate in various dimensions are discussed. Our results are applicable both to cosmological DWs and to the braneworld models.