sentences:  In fact, some theoretical models incorporate a hydrodynamical instability in the stalled shock known as the "Standing Accretion Shock Instability" (SASI).This instability comes about as a consequence of non-spherical perturbations oscillating the stalled shock thereby deforming it.The SASI is often used in tandem with neutrino theories in computer simulations for re-energizing the stalled shock.