Influence of multiple scattering on the radiation of relativistic particles in amorphous and crystalline media

The article sets forth the theory of the influence of multiple scattering on the radiation of ultrarelativistic particles in matter. The classical theory of the Landau-Pomeranchuk effect of suppression of the radiation of relativistic particles in an amorphous medium is presented both in the simple form given by the authors and in a refined form due to Migdal. It is shown that in investigation of the influence of multiple scattering on the radiation of fast particles in matter it is possible to use a functional integration method which permits construction of a quantitative theory of the effect in both amorphous and crystalline media. The question of the possibility of stochastic motion of fast charged particles in a crystal is discussed. The general regularities and distinctive features in processes of radiation of relativistic particles in amorphous and crystalline media and also in intense external electromagnetic fields are discussed.