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. PGR can be relevant in the infrared part of the spectrum of the relic gravitons where radiation from the collapsed DWs is damped.
Highlights
Either must be unstable, what happens if the discrete symmetry was only approximate, or disappear via some other mechanism
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 Domain wall (DW), 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
The holes in the DWs could be created by bulk black holes perforating them [21], so physics of perforation is worth to be explored in detail
Summary
We consider the gravitating system of an infinite Nambu-Goto DW of plain topology and a point particle. Omitting the self-gravity of each object, we treat the full metric generated by them via Einstein equations and the motion of both objects in this metric self-consistently in the framework of the perturbation theory on the Minkowski background in terms of the coupling constant κ (κ2 = 16πGD), where GD is the D-dimensional Newton constant (we use the units c = 1). When gravity is switched off, the following geometry of the collision is assumed: the plane infinite Nambu-Goto brane sits at rest in D-dimensional Minkowski space-time, so that its world-volume is orthogonal to z-axis. Mass m is moving along z-axis with some initial velocity such that it reaches the wall and perforates it. Our conventions for the Riemann and Ricci tensors are: RBNRS ≡ ΓBNS,R − ΓBNR,S + ΓANSΓBAR − ΓANRΓBAS and RMN ≡ δAB RAMBN
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