Dispersive censor of acoustic spacetimes with a shock-wave singularity

Abstract

A dispersionless shock wave in a fluid without friction develops an acoustic spacetime singularity which is naked (not hidden by a horizon). We show that this naked nondispersive shock-wave singularity is prohibited to form in a Bose-Einstein condensate, due to the microscopic structure of the underlying ${\rm a}\!{\rm e}$ther and the resulting effective trans-Planckian dispersion. Approaching the instant of shock $t_{\rm shock}$, rapid spatial oscillations of density and velocity develop around the shock location, which begin to emerge already slightly before $t_{\rm shock}$, due to the quantum pressure in the condensate. These oscillations render the acoustic spacetime structure completely regular, and therefore lead to a removal (censoring) of the spacetime singularity. Thus, distinct from the cosmic censorship hypothesis of Penrose formulated within Einsteinian gravity, the quantum pressure in Bose-Einstein condensates censors (prohibits) the formation of a naked shock-wave singularity, instead of hiding it behind a horizon.