title: Comment on "Lifshitz-Matsubara sum formula for the Casimir pressure between magnetic metallic mirrors".
abstract: Recently Guérout et al. [Phys. Rev. E 93, 022108 (2016)1539-375510.1103/PhysRevE.93.022108] 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 for 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.
authors.affiliation: Central Astronomical Observatory at Pulkovo of the Russian Academy of Sciences, Saint Petersburg 196140, Russia and Institute of Physics, Nanotechnology and Telecommunications, Peter the Great Saint Petersburg Polytechnic University, St. Petersburg 195251, Russia.
authors.forename: G L
authors.initials: GL
authors.lastname: Klimchitskaya
authors.affiliation: Central Astronomical Observatory at Pulkovo of the Russian Academy of Sciences, Saint Petersburg 196140, Russia and Institute of Physics, Nanotechnology and Telecommunications, Peter the Great Saint Petersburg Polytechnic University, St. Petersburg 195251, Russia.
authors.forename: V M
authors.initials: VM
authors.lastname: Mostepanenko