  We investigate photon pair-creation in a dispersive dielectric medium induced
by the presence of a spacetime varying dielectric constant. Our aim is to
examine the possibility to observe new phenomena of pair creation induced by
travelling dielectric perturbations e.g. created by laser pulses by means of
the Kerr effect. In this perspective, we adopt a semi-phenomenological version
of the Hopfield model in which a space-time dependent dielectric susceptibility
appears. We focus our attention on perturbation theory, and provide general
formulas for the photon production induced by a local but arbitrarily spacetime
dependent refractive index perturbation. As an example, we further explore the
case of an uniformly travelling perturbation, and provide examples of purely
time-dependent perturbations.
