Slow scrambling in sonic black holes

We study from the perspective of quantum information scrambling an acoustic black hole modeled by two semi-infinite, stationary, one-dimensional condensates, connected by a spatial step-like discontinuity, and flowing, respectively, at subsonic and supersonic velocities. We develop a simple analytical treatment based on the Bogoliubov theory of quantum fluctuations which is sufficient to derive an analogue Hawking emission, and we compute out-of-time order correlations (OTOCs) of the Bose density field. We find that a large class of sonic black holes presents slow scrambling contrary to their astrophysical counterparts. This manifests itself in a power law growth t2 of OTOCs in contrast to the exponential increase in time expected for fast scramblers.