  The instabilities arising in a one-dimensional beam sustained by the
diffusive photorefractive nonlinearity in out-of-equilibrium ferroelectrics are
theoretically and numerically investigated. In the "scale-free model", in
striking contrast with the well-known spatial modulational instability, two
different beam instabilities dominate: a defocusing and a fragmenting process.
Both are independent of the beam power and are not associated to any specific
periodic pattern.
