Evolution of a steady state of the two-dimensional Gross-Pitaevskii equation

Expansion of a steady state of the Gross–Pitaevskii equation after switching off the external field has been investigated. It has been shown that the evolution of the aspect ratio of the localized solution is described by the one-dimensional oscillator equation with renormalized time. The renormalization is determined by the evolution of the width or the second moment of the solution. It has been found that the aspect ratio is monotonically inverted in infinite time in the case of the linear Schrödinger equation and does not reach the inverse value in the nonlinear case.