Electrodynamics of massless charged particles

Lechner, Kurt

doi:10.1063/1.4906813

Cited by 19 publications

(21 citation statements)

References 23 publications

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“…It was argued that the line singularity of the Lienard-Wiechert potential for the massless charge forbids using the Green function method to compute radiation [1,2], while, according to [3], the conservation equation for Maxwell energy-momentum tensor implies that the massless charge does not radiate at all [3]. The similar assertion was earlier formulated by Kosyakov [4] basing on conformal invariance of classical electrodynamics with massless charges (see also [5]).…”

Section: Introductionmentioning

confidence: 83%

Synchrotron radiation from massless charge

Gal’tsov

2015

Physics Letters B

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Classical radiation power from an accelerated massive charge diverges in the zero-mass limit, while some authors suggest that strictly massless charge does not radiate at all. On the other hand, the regularized classical radiation reaction force, though looking odd, is non-zero and finite. To clarify this controversy, we consider radiation problem in massless scalar quantum electrodynamics in the external magnetic field. In this framework, synchrotron radiation is found to be non-zero, finite, and essentially quantum. Its spectral distribution is calculated using Schwinger's proper time technique for ab initio massless particle of zero spin. Provided E 2 eH, the maximum in the spectrum is shown to be at hω = E/3, and the average photon energy is 4E/9. The normalized spectrum is universal, depending neither on E nor on H. Quantum nature of radiation makes classical radiation reaction equation meaningless for massless charge. Classical theory is reliable only as providing the low-frequency part of the true quantum radiation spectrum.

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Section: Introductionmentioning

confidence: 83%

Synchrotron radiation from massless charge

Gal’tsov

2015

Physics Letters B

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“…This is the well-known collinear divergence encountered in quantum perturbation theory for interacting massless particles. In classical theory this is the line divergence of the retarded potentials [66].…”

Section: The Particle Amplitudementioning

confidence: 99%

Piercing of domain walls: new mechanism of gravitational radiation

Gal’tsov

Melkumova

Spirin

2018

J. High Energ. Phys.

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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.

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“…As far as the problem of radiation from massless sources is concerned, the arguments were presented that radiation in this case is totally absent [26,27]. Indeed, within the classical theory the retarded potentials from massless point sources diverge on a line parallel to the velocity, and various ways to regularize these divergences -which also have quantum counterparts as collinear divergences [28][29][30][31] -were suggested.…”

Section: Introductionmentioning

confidence: 99%

Branestrahlung: Radiation in the particle-brane collision

2016

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We calculate the radiation accompanying the gravitational collision of a domain wall a the point particle in five-dimensional spacetime. This process -which can be regarded as brane-particle bremsstrahlung, here called 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 nontrivial, 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 nonzero and has classically divergent spectrum. We estimate the total radiation power introducing appropriate cutoffs. In passing, we explain how the sum of the nonlocal (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 defines a regular functional.

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Electrodynamics of massless charged particles

Cited by 19 publications

References 23 publications

Synchrotron radiation from massless charge

Synchrotron radiation from massless charge

Piercing of domain walls: new mechanism of gravitational radiation

Branestrahlung: Radiation in the particle-brane collision

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