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We present a theoretical study on the origin of some findings of recentexperiments on sonic analogs of gravitational black holes. We focus on therealization of a black-hole lasing configuration, where the conclusiveidentification of stimulated Hawking radiation requires dealing with theimplications of the nonstationary character of the setup. To isolate the basicmechanisms responsible for the observed behavior, we use a toy model wherenonstationarity can be described in terms of departures from adiabaticity. Ourapproach allows studying which aspects of the characterization of black-holelasing in static models are still present in a dynamical scenario. Inparticular, variations in the role of the dynamical instabilities can betraced. Arguments to conjecture the twofold origin of the detectedamplification of sound are given: the differential effect of the instabilitieson the mean field and on the quantum fluctuations gives some clues to separatea deterministic component from self-amplified Hawking radiation. The role ofclassical noise, present in the experimental setup, is also tackled: we discussthe emergence of differences with the effect of quantum fluctuations whenvarious unstable modes are relevant to the dynamics.

Black-hole lasing in Bose-Einstein condensates: analysis of the role of the dynamical instabilities in a nonstationary setup