Abstract
We analyze how the frequency dependence of the electric permittivity ε affects the electromagnetic field radiated by a point charge uniformly moving in a medium. Various limiting cases are studied analytically and confirmed numerically. It turns out that a moving charge radiates at every velocity when the standard parametrization of ε is chosen. The space distribution of this radiation exhibits rapid oscillations behind the moving charge. They differ drastically for charge velocities below and above some critical velocity νc defined by the medium properties and independent of frequency. It turns out that for ν < νc the radiation flux is maximal at the same place where in the absence of ω dispersion lies in the Cherenkov radiation singular cone. For ν < νc the radiation flux is maximal behind the moving charge on a sufficiently remote distance. This consideration is applied to the interpretation of experiments recently discussed in physical literature.