Problem of bremsstrahlung in: The case of gravitational interaction

2018

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.

Section: Jhep01(2018)120mentioning

confidence: 99%

Piercing of domain walls: new mechanism of gravitational radiation

Gal’tsov

Melkumova

2018

“…The difference is related with the erroneous neglect of the local current (which turns out to be significant) at the dominant frequency ω ∼ γ/b in [59], whereas it has the same magnitude as the non-local part which is retained. Because of this, the total coefficient is determined with an error, as well as the small-and medium-frequency behavior.…”

Section: Jhep01(2014)111mentioning

confidence: 98%

“…Among the previous works in four dimensions on the electromagnetic radiation caused by gravitational force, one emphasizes the papers by Peters [42], by Matzner and Nutku [58] and the work by Gal'tsov, Grats and Matyukhin [59]. In [42] the post-linear formalism is used in the coordinate space for Schwarzschild background, considering bremsstrahlung near the vicinity of black hole.…”

Section: Jhep01(2014)111mentioning

confidence: 99%

“…In [58] the equivalentphotons method was adapted for gravitons. This approach was criticized in [59], who found that this method is of limited range when the frequency range is decreased γ times, and thereby inappropriate.…”

Section: Jhep01(2014)111mentioning

confidence: 99%

“…In [59] the iteration scheme accompanied by the perturbation theory is used -as well as in the present work, while mathematical techniques are different: contour integration in [59] versus expansion of Macdonald functions here. The similar features are: (i) the damping of radiation amplitude at high frequencies ω ∼ γ 2 /b (at Lab frame), (ii) the significant frequency ω ∼ γ/b, coming from the partial cancelation of local and non-local currents, and (iii) the final power of Lorentz factor:…”

Section: Jhep01(2014)111mentioning

confidence: 99%

See 2 more Smart Citations

Vector bremsstrahlung by ultrarelativistic collisions in higher dimensions

Constantinou

2014

A classical computation of vector bremsstrahlung in ultrarelativistic gravitational-force collisions of massive point particles is presented in an arbitrary number d of extra dimensions. Our method adapts the post-linear formalism of General Relativity to the multidimensional case. The total emitted energy, as well as its angular and frequency distribution and characteristic values, are discussed in detail.For an electromagnetic mediation propagated in the bulk, the emitted energy E em of scattering with impact parameter b has magnitude E em ∼ e 4 e ′ 2 γ d+2 /(m 2 b 3d+3 ), with dominant frequency ω em ∼ γ 2 /b. For the gravitational force the charge emits via vector field, propagated in the bulk, energy Finally, for the ADD model, including four dimensions, the electromagnetic field living on 3-brane, loses on emission the energyThe contribution of the low frequency part of the radiation (soft photons) to the total radiated energy is shown to be negligible for all values of d. The domain of validity of the classical result is discussed. The result is analyzed from the viewpoint of the de WittBrehme-Hobbs equation (and corresponding equations in higher dimensions). The different frequency domains and their competition mentioned above, may be explained as coming from different terms in this equation. Thus the whole emission process may be naturally split in two sub-processes with drastically different spectral and temporal characteristics.

Gravitational bremsstrahlung in ultra-planckian collisions

Gal'Tsov

Tomaras

2013

A classical computation of gravitational bremsstrahlung in ultra-planckian collisions of massive point particles is presented in an arbitrary number d of toroidal or non-compact extra dimensions. Our method generalizes the post-linear formalism of General Relativity to the multidimensional case. The total emitted energy, as well as its angular and frequency distribution are discussed in detail. In terms of the gravitational radius r_S of the collision energy, the impact parameter b and the Lorentz factor in the CM frame, the leading order radiation efficiency in the Lab frame is shown to be of order (r_S/b)^{3(d+1)} gamma_{cm} for d=0, 1 and of order (r_S/b)^{3(d+1)} gamma_{cm}^{2d-3} for d>1, up to a known d-dependent coefficient and a ln gamma_{cm} factor for d=2, while the characteristic frequency of the radiation is gamma/b. The contribution of the low frequency part of the radiation (soft gravitons) to the total radiated energy is shown to be negligible for all values of d. The domain of validity of the classical result is discussed. Finally, it is shown that within the region of validity of our approach the efficiency can obtain unnatural values greater than one, which is interpreted to mean that the peripheral ultra-planckian collisions should be strongly radiation damped.Comment: 38 pages, 5 figure