Spontaneous particle creation in time-dependent overcritical fields

TL;DR

This paper investigates how strong, time-dependent overcritical electromagnetic fields can cause spontaneous electron-positron pair creation, clarifying the conditions under which this phenomenon is well-defined and stable.

Contribution

It extends the understanding of vacuum instability by analyzing particle creation in dynamic overcritical fields, providing a framework for measurement and stability conditions.

Findings

Spontaneous pair creation occurs when overcritical fields are switched on.

The effect is unstable and approximate when fields are switched on and off.

In the adiabatic limit, the particle creation becomes stable and well-defined.

Abstract

It is believed that in presence of some strong electromagnetic fields, called overcritical, the (Dirac) vacuum becomes unstable and decays leading to a spontaneous production of an electron-positron pair. Yet, the arguments are based mainly on the analysis of static fields and are insufficient to explain this phenomenon completely. Therefore, we consider time-dependent overcritical fields and show, within the external field formulation, how spontaneous particle creation can be defined and measured in physical processes. We prove that the effect exists always when a strongly overcritical field is switched on, but it becomes unstable and hence generically only approximate and non-unique when the field is switched on and off. In the latter case, it becomes unique and stable only in the adiabatic limit.