Genericity property of comoving potentials art. no. 033604

Comoving potentials or refractive indices acting on the propagation of wave s of various nature are shown to exhibit a resonant effect giving rise to a general property we call genericity in the sense that they provide a phase shift with any desired dependence on the momentum. Application in atom opt ics to balance the natural spreading of matter waves in a vacuum is given. Optical analogies are also examined in view of applications in coherent con trol of short pulses.