  We theoretically investigate superradiance effects in quantum field theories
in curved space-times by proposing an analogue model based on Bose--Einstein
condensates subject to a synthetic vector potential. The breaking of the
irrotationality constraint of superfluids allows to study superradiance in
simple planar geometries and obtain intuitive insight in the amplified
scattering processes at ergosurfaces. When boundary conditions are modified
allowing for reflections, dynamical instabilities are found, similar to the
ones of ergoregions in rotating space-times. Their stabilization by horizons in
black hole geometries is discussed. All these phenomena are reinterpreted
through an exact mapping with the physics of one-dimensional relativistic
charged scalar fields in electrostatic potentials. Our study provides a deeper
understanding on the basic mechanisms of superradiance: by disentangling the
different ingredients at play, it shines light on some misconceptions on the
role of dissipation and horizons and on the competition between superradiant
scattering and instabilities.
