Signatures of the Schwinger mechanism assisted by a fast-oscillating electric field

Abstract

The spontaneous production of electron-positron pairs from the vacuum---in a field configuration composed of a high-frequency electric mode of weak intensity and a strong constant electric field---is investigated. Asymptotic expressions for the single-particle distribution function ruling this nonperturbative process are established by considering the low-density approximation in the Boltzmann-Vlasov equation. An analytical formula for the density rate of yielded particles is established and is shown to manifest a nonperturbative dependence on both the strong and weak electric fields and to generalize previous findings by interpolating between the tunneling and multiphoton regimes. It is shown that---under appropriate circumstances---the created plasma of electrons and positrons might reach densities for which their recombinations into high-energy photons occurs copiously. On the basis of this feature, an experimental setup for observing the dynamically assisted Schwinger effect is put forward.