Displaying 341 – 360 of 441

Showing per page

Symmetries of the nonlinear Schrödinger equation

Benoît Grébert, Thomas Kappeler (2002)

Bulletin de la Société Mathématique de France

Symmetries of the defocusing nonlinear Schrödinger equation are expressed in action-angle coordinates and characterized in terms of the periodic and Dirichlet spectrum of the associated Zakharov-Shabat system. Application: proof of the conjecture that the periodic spectrum < λ k - λ k + < λ k + 1 - of a Zakharov-Shabat operator is symmetric,i.e. λ k ± = - λ - k for all k , if and only if the sequence ( γ k ) k of gap lengths, γ k : = λ k + - λ k - , is symmetric with respect to k = 0 .

The cubic Szegő equation

Patrick Gérard, Sandrine Grellier (2010)

Annales scientifiques de l'École Normale Supérieure

We consider the following Hamiltonian equation on the L 2 Hardy space on the circle, i t u = Π ( | u | 2 u ) , where Π is the Szegő projector. This equation can be seen as a toy model for totally non dispersive evolution equations. We display a Lax pair structure for this equation. We prove that it admits an infinite sequence of conservation laws in involution, and that it can be approximated by a sequence of finite dimensional completely integrable Hamiltonian systems. We establish several instability phenomena illustrating...

Currently displaying 341 – 360 of 441