The multi-dimensional character and mechanisms of core-collapse supernovae

On this twentieth anniversary of the epiphany of SN1987A, we summarize various proposed explosion mechanisms for the generic core-collapse supernova. Whether the agency is neutrinos, acoustic power, magnetohydrodynamics, or some hybrid combination of these three, both multi-dimensional simulations and constraining astronomical measurements point to a key role for asphericities and instabilities in collapse and explosion dynamics. Moreover, different progenitors may explode in different ways, and have different observational signatures. Whatever these are, the complex phenomena being revealed through modern multi-dimensional numerical simulations manifest a richness that was little anticipated in the early years of theoretical supernova research, a richness that continues to challenge us today.