ABSTRACT
Tamm started discussing one of my first papers devoted to the quantum theory of Vavilov-Cherenkov (VC) radiation. I had shown that the conditions for the emission of this radiation follow when one applies the laws of conservation of energy and momentum to a particle radiating a photon of energy 1i.w and momentum li.wn/ c, where n(w) is the refractive index of the medium.6* I, of course, had also calculated the intensity of the VC radiation but we did not come up with the intensity at that seminar. Landau immediately expressed skepticism about my results, saying that they were of no interest since the effect is classical and there was no point in treating it quantum mechanically. He was right in some sense, because quantum corrections in the problem of VC radiation are of order li.w/mc2 (m is the particle mass) and are, therefore, small in the optical region. But very often a new interpretation, approach, or conclusion turns out to be fruitful. This was the case in my work on VC radiation: the quantum approach and the use of the conservation laws appeared to yield new results in, for example, studies of the Doppler effect in a dispersive medium. 6*
I have dwelt on this experience with Landau, first, to demonstrate once again his pragmatism and his dislike for 'Neubegrundung'. Second, this example is a striking illustration of the role of tastes and feeling in science. I literally love problems dealing with VC radiation and, generally, with radiation emitted by uniformly moving sources. Landau was quite indifferent to this range of questions and did not consider the VC effect beautiful. This incident is not the only illustration of this predilection: I remember telling Landau about a paper-! think it was the paper by D Bohm and D Pines (or E P Gross)-in which the plasma (longitudinal) wave damping discovered by Landau was interpreted as the inverse VC effect. But Landau remained quite indifferent to this interpretation.
