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Recent hydrodynamical calculations in multidimension have shown that conditions following core collapse lead to a radical break of the initially prevailing spherical symmetry. Neutrinos emerging from the hot protoneutron star heat the surrounding matter thereby inducing violent convection. Contrary to what a mixing-length approach suggests, the convective motions are coherent on large scales. This allows a thermodynamical cycle to be established as matter infalling and bubbling up travels in a loop through the $PV$ plane. Work is therefore extracted in a way impossible in a one-dimensional picture for which thermodynamic quantities can only be single valued functions of radius. In the convective engine model for SN explosions, the supernova is likened to an open cycle thermodynamic engine in which a reservoir of low-entropy matter (the envelope) is thermally coupled and physically connected to a hot bath (the protoneutron star) by a neutrino flux, and by hydrodynamic instabilities. The paradigm is appealing because it predicts successful explosions of the appropriate magnitude, without invoking new physics or fine tuning old physics. However, it potentially ejects neutron-rich material in undesirable quantities. This issue is intimately connected to the fall-back of matter onto the protoneutron star following the explosion which remains to be investigated properly. Also open is the question of how and when a black hole might form. In my talk, I will try to better define these questions so as to put them on the table for further discussion.
