Branestrahlung: radiation in the particle-brane collision

TL;DR

This paper investigates the unique radiation phenomena, called branestrahlung, occurring during the collision of a domain wall and a point particle in five-dimensional spacetime, revealing non-trivial light-like radiation effects.

Contribution

It provides a detailed analysis of radiation from brane-particle collisions, including the effects of shock branon waves and the non-zero radiation from light-like sources in five dimensions.

Findings

Radiation includes shock branon waves expanding at light speed.

Light-like sources can produce non-zero, divergent radiation spectra.

Total radiation power estimated with appropriate cutoffs.

Abstract

We calculate the radiation accompanying gravitational collision of the domain wall and the point particle in five-dimensional spacetime. This process, which can be regarded as brane-particle bremsstrahlung, here called {\it branestrahlung}, has unusual features. Since the brane has intrinsic dynamics, it gets excited in the course of collision, and, in particular, at the moment of perforation the shock branon wave is generated, which then expands with the velocity of light. Therefore, apart from the time-like source, whose radiation can be computed in a standard way, the total radiation source contains a light-like part whose retarded field is quite non-trivial, exhibiting interesting retardation and memory effects. We analyze this field in detail, showing that, contrary to the claims that the light-like sources should not radiate at all, the radiation is non-zero and has classically divergent spectrum. We estimate the total radiation power introducing appropriate cutoffs. In passing, we explain how the sum of the non-local (with the support inside the light cone) and the local (supported on the cone) singular parts of the Green's function of the five-dimensional d'Alembert equation together define a regular functional.