Afterglow of the dynamical Schwinger process: soft photons amass

TL;DR

This paper investigates how the dynamical Schwinger process generates soft photons in electric fields, revealing that a significant number of optical-range photons accumulate, which could be detected in upcoming laser experiments.

Contribution

It introduces a method to analyze photon production as a secondary probe of the dynamical Schwinger process, highlighting the accumulation of soft photons in the optical range.

Findings

Soft photons amass in the optical range during the Schwinger process.

Photon production occurs even in sub-critical electric fields.

Potential for experimental detection with upcoming laser facilities like ELI-NP.

Abstract

We consider the conversion of an electric field into photons as a secondary probe of the dynamical Schwinger process. In spatially homogeneous electric fields, quantum fluctuations of electron-positron ($e^+e^-$) pairs are lifted on the mass shell leaving asymptotically a small finite pair density. The $e^+e^-$ dynamics in turn couples to the quantized photon field and drives its on-shell mode occupation. The spectral properties of the emerging asymptotic photons accompanying the Schwinger process are calculated in lowest-order perturbation theory. Soft photons in the optical range are produced amass in the sub critical region, thus providing a promising discovery avenue, e.g. for laser parameters of the Extreme Light Initiative (ELI-NP) to be put in operation soon.