Impact of trans-Planckian excitations on black-hole radiation in dipolar condensates

We consider a quasi-one-dimensional dipolar condensate in an analogue black hole setup. It is shown that the existence of a roton minimum in the condensate dispersion relation leaves deep imprints onto the Hawking radiation spectrum. In particular, the emitted radiation can be either more intense or suppressed, depending on the depth of the roton minimum in the excitation spectrum. In addition, we find that spontaneous particle creation occurs even when the horizon is removed. Our results establish that dipolar condensates offer a richer and more versatile environment for the simulation of particle production from the quantum vacuum in the presence of horizon-interfaces than their contact-interaction counterparts.