Stability of periodic waves of 1D cubic nonlinear Schr{\"o}dinger equations

TL;DR

This paper investigates the stability properties of various periodic wave solutions to the 1D cubic nonlinear Schrödinger equation, providing new proofs, stability criteria, and numerical methods to understand their behavior under perturbations.

Contribution

It offers new variational characterizations, proves spectral stability for cnoidal waves, and develops numerical techniques, advancing understanding of periodic wave stability in nonlinear Schrödinger equations.

Findings

Orbital stability of cnoidal, dnoidal, and snoidal waves established.

Spectral stability of cnoidal waves proven in certain parameter ranges.

Numerical methods support analytical stability and instability results.

Abstract

We study the stability of the cnoidal, dnoidal and snoidal elliptic functions as spatially-periodic standing wave solutions of the 1D cubic nonlinear Schr{\"o}dinger equations. First, we give global variational characterizations of each of these periodic waves, which in particular provide alternate proofs of their orbital stability with respect to same-period perturbations, restricted to certain subspaces. Second, we prove the spectral stability of the cnoidal waves against same-period perturbations (in a certain parameter range), and provide an alternate proof of this (known) fact for the snoidal waves, which does not rely on complete integrability. Third, we give a rigorous version of a formal asymptotic calculation of Rowlands to establish the instability of a class of real-valued periodic waves in 1D, which includes the cnoidal waves of the 1D cubic focusing nonlinear Schr{\"o}dinger equation, against perturbations with period a large multiple of their fundamental period. Finally, we develop a numerical method to compute the minimizers of the energy with fixed mass and momentum constraints. Numerical experiments support and complete our analytical results.