Modified vacuum polarization in the presence of a plasma

TL;DR

This paper investigates how a plasma affects vacuum polarization in strong fields, revealing quantum modifications and the interplay between real particles and virtual particles in the evolution of the Dirac field.

Contribution

It introduces a quantum kinetic framework to analyze vacuum polarization in plasma, highlighting the impact of real particle content on quantum corrections.

Findings

Quantum kinetic equations describe Dirac field evolution with classical-like distributions.

Vacuum polarization includes known expressions plus quantum modifications from real particles.

The dominant quantum correction source depends on plasma density.

Abstract

We study vacuum polarization due to strong fields, in the presence of an electron-positron plasma. For this purpose, we expand quantum kinetic equations using weak fields and slow temporal scales as expansion parameters. It is demonstrated that the evolution of the Dirac field can be described by classical-like distribution functions for electrons and positrons, which are weakly coupled through quantum interactions. Furthermore, we deduce that these coupling terms give rise to well-known expressions for vacuum polarization, in addition to quantum modifications proportional to the content of real particles. Depending on the initial plasma density, the dominant quantum corrections to classical evolution may arise from real particle couplings or from the vacuum polarization associated with virtual particles. The implications of our results are discussed.