Backreaction in Acoustic Black Holes

The backreaction equations for the linearized quantum fluctuations in an acoustic black hole are given. The solution near the horizon, obtained within a dimensional reduction, indicates that acoustic black holes, unlike Schwarzschild ones, get cooler as they radiate phonons. They show remarkable analogies with near-extremal Reissner-Nordström black holes.

Figure 1

A Laval nozzle. The waist of the nozzle represents the sonic horizon ($|{\overrightarrow{v}}_0|=c$). In the region on the right of the waist $|{\overrightarrow{v}}_0|<c$, and on the left $|{\overrightarrow{v}}_0|>c$ (sonic hole).