Quantum unitary dynamics of a charged fermionic field and Schwinger effect

TL;DR

This paper investigates the quantum dynamics of a charged fermionic field in a time-dependent electric field, establishing a unique class of quantizations that ensure a consistent particle creation description over time.

Contribution

It extends previous scalar field analyses to fermionic fields, characterizing unique quantizations that preserve symmetries and unitarity in particle creation processes.

Findings

Identifies a unique class of unitarily equivalent quantizations for fermionic fields.

Provides a well-defined particle number at all finite times.

Extends symmetry-preserving quantization methods to charged fermionic fields.

Abstract

In quantum field theory, particle creation occurs, in general, when an intense external field, such as an electromagnetic field, breaks time translational invariance. This leads to an ambiguity in the definition of the vacuum state. In cosmological backgrounds this ambiguity has been reduced by imposing that the quantization preserves the symmetries of the system and that the dynamics is unitarily implemented. In this work, we apply these requirements to the quantization of a massive charged fermionic field coupled to a classical time-dependent homogeneous electric field, extending previous studies done for a scalar field. We characterize the quantizations fulfilling the criteria above and we show that they form a unique equivalence class of unitarily related quantizations, which provide a well-defined number of created particles at all finite times.