Comment on "low-frequency character of the Casimir force between metallic films"

In Phys. Rev. E 70, 047102 (2004), Torgerson and Lamoreaux investigated for the first time the real-frequency spectrum of the finite temperature correction to the Casimir force, for metallic plates of finite conductivity. The very interesting result of this study is that the large correction from the TE mode is dominated by low frequencies, for which the dielectric description of the metal is invalid, and the authors correctly point out that a more realistic description is provided by low-frequency metallic boundary conditions. However, their subsequent analysis uses an incorrect form of metallic boundary conditions for TE modes. After correcting this error, we find that their main conclusion was nevertheless qualitatively correct: contrary to the result of the dielectric model, the thermal TE mode correction leads to an increase in the TE mode force of attraction between the plates. The correction found by us, however, has a magnitude about 20 times larger than that quoted by Torgerson and Lamoreaux.