Abstract
A charged particle moving through a medium emits Cherenkov radiation when its velocity exceeds the phase velocity of light in that medium. Under the influence of a strong electromagnetic field, quantum fluctuations can become polarized, imbuing the vacuum with an effective anisotropic refractive index and allowing the possibility of Cherenkov radiation from the quantum vacuum. We analyze the properties of this vacuum Cherenkov radiation in strong laser pulses and the magnetic field around a pulsar, finding regimes in which it is the dominant radiation mechanism. This radiation process may be relevant to the excess signals of high energy photons in astrophysical observations.
Highlights
A charged particle moving through a medium emits Cherenkov radiation when its velocity exceeds the phase velocity of light in that medium
An early prediction of Quantum electrodynamics (QED) is the presence of virtual particleantiparticle pairs which fluctuate in and out of existence in the quantum vacuum
It has been known since the seminal work of Euler and Heisenberg [1] that a strong electromagnetic field can polarize these vacuum fluctuations
Summary
A charged particle moving through a medium emits Cherenkov radiation when its velocity exceeds the phase velocity of light in that medium. Since vacuum fluctuations can reduce the phase velocity of light (see, for example, [14]), the same argument implies that high-energy particles traveling through strong electromagnetic fields should emit Cherenkov radiation, in addition to the usual synchrotron radiation caused by acceleration in the field. The generalization of the Cherenkov angle to nonlinear electrodynamics is straightforward: it retains the form given in (7), but the anisotropy of the background field implies the phase velocity itself depends on the direction of emission, vp 1⁄4 vpðkÞ.
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