  We show that particle creation of Bogoliubov modes in a Bose-Einstein
condensate due to the accelerated motion of the trap is a genuinely
relativistic effect. To this end we show that Bogoliubov modes can be described
by a time rescaling of the Minkowski metric. A consequence of this is that
Rindler transformations are perceived by the phonons as generalised Rindler
transformations where the speed of light is replaced by the speed of sound,
enhancing particle creation at small velocities. Since the non-relativistic
limit of a Rindler transformation is just a Galilean transformation entailing
no length contraction or time dilation, we show that the effect vanishes in the
non-relativistic limit.
