Exact WKB analysis of the vacuum pair production by time-dependent electric fields

We study the vacuum pair production by a time-dependent strong electric field based on the exact WKB analysis. We identify the generic structure of a Stokes graph for systems with the vacuum pair production and show that the number of produced pairs is given by a product of connection matrices for Stokes segments connecting pairs of turning points. We derive an explicit formula for the number of produced pairs, assuming the semi-classical limit. The obtained formula can be understood as a generalization of the divergent asymptotic series method by Berry, and is consistent with other semi-classical methods such as the worldline instanton method and the steepest descent evaluation of the Bogoliubov coefficients done by Brezin and Izykson. We also use the formula to discuss effects of time-dependence of the applied strong electric field including the interplay between the perturbative multi-photon pair production and non-peturbative Schwinger mechanism, and the dynamically assisted Schwinger mechanism.

On the instability of localized EM pulses in nonlinear electrodynamics with account of temperature effects

Based on Maxwell’s equations, we study the development of electromagnetic pulse instability in nonlinear electrodynamics beyond approximation of slowly varying amplitudes and phases. The action was chosen from the Heisenberg–Euler Lagrangian based on the invariants of the electromagnetic field. We analyze the scenario for the evolution of instability, which turns out to be consistent with the earlier conclusion done within the approximation of slowly varying amplitudes and phases. In this study, we take into account the influence of temperature. The rate of pair production under the Schwinger mechanism is estimated.

Chirality production with mass effects — Schwinger pair production and the axial Ward identity

The anomalous generation of chirality with mass effects via the axial Ward identity and its dependence on the Schwinger mechanism is reviewed, utilizing parity violating homogeneous electromagnetic background fields. The role vacuum asymptotic states play on the interpretation of expectation values is examined. It is discussed that observables calculated with an in–out scattering matrix element predict a scenario under Euclidean equilibrium. A notable ramification of which is a vanishing of the chiral anomaly. In contrast, it is discussed observables calculated under an in–in, or real-time, formalism predict a scenario out-of equilibrium, and capture effects of mean produced particle–antiparticle pairs due to the Schwinger mechanism. The out-of equilibrium chiral anomaly is supplemented with exponential quadratic mass suppression as anticipated for the Schwinger mechanism. Similar behavior in and out-of equilibrium is reviewed for applications including the chiral magnetic effect and chiral condensate.

Extremely short optical pulses and superstrings

We analyze the propagation of an extremely short optical pulse from the numerical solution of the Maxwell’s equation related to the effective action obtained in the framework of the theory of superstrings in flat time space. The pulse dynamics turned out to be unstable and eventually leads to a collapse. We particularly analyze the Schwinger mechanism which occurs during the collapse of the pulse.