Universal dynamics for the defocusing logarithmic Schrodinger equation

TL;DR

This paper studies the large-time behavior of solutions to the defocusing logarithmic Schrödinger equation, revealing faster dispersion, logarithmic growth of Sobolev norms, and convergence to a universal Gaussian profile, using a novel analytical approach.

Contribution

It introduces a new analysis of the logarithmic Schrödinger equation's dynamics, showing universal Gaussian convergence and linking it to a Fokker-Planck type equation.

Findings

Dispersion is faster than usual by a logarithmic factor in time.

Sobolev norms grow logarithmically over time.

Solutions converge to a universal Gaussian profile after rescaling.

Abstract

We consider the nonlinear Schrodinger equation with a logarithmic nonlinearity in a dispersive regime. We show that the presence of the nonlinearity affects the large time behavior of the solution: the dispersion is faster than usual by a logarithmic factor in time and the positive Sobolev norms of the solution grow logarithmically in time. Moreover, after rescaling in space by the dispersion rate, the modulus of the solution converges to a universal Gaussian profile. These properties are suggested by explicit computations in the case of Gaussian initial data, and remain when an extra power-like nonlinearity is present in the equation. One of the key steps of the proof consists in using the Madelung transform to reduce the equation to a variant of the isothermal compressible Euler equation, whose large time behavior turns out to be governed by a parabolic equation involving a Fokker-Planck operator.