Comment on "Lifshitz-Matsubara sum formula for the Casimir pressure between magnetic metallic mirrors"

TL;DR

This paper critiques a recent claim that the plasma model must be redefined as a limit of the Drude model for Casimir pressure calculations, arguing that the redefinition is physically invalid and explaining why the traditional plasma model remains appropriate.

Contribution

The paper refutes the proposed redefinition of the plasma model and clarifies its validity in Casimir pressure computations despite mismatches with optical properties.

Findings

The redefinition does not meet physical dielectric requirements.

The plasma model accurately describes Casimir pressure without matching optical data.

The critique clarifies the theoretical basis of the plasma model in Casimir physics.

Abstract

Recently Guerout et al. [Phys. Rev. E, v.93, 022108 (2016)] advocated that the lossless plasma model has to be redefined as the limit of the Drude model when the relaxation parameter goes to zero. It was claimed that the previously used plasma model cannot correctly describe the Casimir pressure between two plates made of both nonmagnetic and magnetic metals and has to be replaced with the redefined one. We show that the suggested redefinition does not satisfy necessary physical requirements imposed on the dielectric permittivity. We also present a plausible explanation to the fact that the lossless plasma model describes the Casimir pressure correctly even though it does not match the optical and electrical properties of metals.