Abstract
Sharp sufficient criteria for collapse are found for the nonlinear Schrödinger equation in the so-called supercritical case as well as for the Ginzburg-Landau equation in the case of the subcritical bifurcation. It is demonstrated that nonstable solitons in these models, under some additional assumptions, play the role of a ‘‘boundary’’ (saddle points) between collapsing and noncollapsing solutions.