title: Comment on "Quantum processes in the field of a two-frequency circularly polarized plane electromagnetic wave".
abstract: We show that there is a mistake in the results recently published by An Yu and H. Takahashi [Phys. Rev. E 57, 2276 (1998)] for the probabilities of a photon emission by an electron and a pair production by a photon in the field of a two-frequency plane electromagnetic wave. In this paper we present the corrected expression for the probability of a photon emission which contains terms missed by Yu and Takahashi. We argue also that the effect of presence of the waves with combination frequencies in the external field proposed by the authors of the paper [Phys. Rev. E 57, 2276 (1998)] has no physical basis.
authors.forename: N B
authors.initials: NB
authors.lastname: Narozhny
authors.forename: M S
authors.initials: MS
authors.lastname: Fofanov