Complex aberration and a new Cerenkov effect for superluminal phase velocities

Moving isotropic media are analyzed considering superluminal phase velocities instead of the usual subluminal regime. The following new effects arise: (i) a complex aberration, i.e., angles that are complex in the proper frame can correspond to real angles in the lab frame; (ii) Cerenkov effect occurs although the usual condition associated with this effect, in which the relative phase velocity is below the velocity between frames, is not verified. Dispersion and losses are mandatory in order to respect causality, therefore, a Lorentz causal dispersive model is considered. We show that losses play a very important role in the superluminal regime. Without losses the predicted effects could occur for non-relativistic velocities between frames.