Nonlinear effects in two-dimensional superfluidHe4

Abstract
A nonlinear finite-amplitude density-wave-propagation equation in two-dimensional superfluid He4 is derived. Though this equation is similar to that investigated by Huberman, it differs in the coefficient of the nonlinear term of the Korteweg—de Vries equation used by him. The conditions are studied for the propagation of solitons in thin superfluid films at low temperatures. Possible experiments are discussed to test the predictions of the theory.