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The Szegö Cubic Equation
Gérard P., Grellier S.
http://hal.archives-ouvertes.fr/hal-00398799
Preprint, Working Paper, ...
Mathematics/Complex Variables
Mathematics/Analysis of PDEs
The Szegö Cubic Equation
Patrick Gérard () 1, Sandrine Grellier () 2
1:  Laboratoire de Mathématiques d'Orsay (LM-Orsay)
http://www.math.u-psud.fr
CNRS : UMR8628 – Université Paris XI - Paris Sud
France
2:  Mathématiques - Analyse, Probabilités, Modélisation - Orléans (MAPMO)
http://www.univ-orleans.fr/mapmo/
Université d'Orléans – CNRS : UMR7349
Fédération Denis Poisson, Bâtiment de Mathématiques, B.P. 6759, 45067 Orléans cedex 2
France
We consider the following Hamiltonian equation on the $L^2$ Hardy space on the circle, $$i\partial _tu=\Pi(|u|^2u)\ ,$$ where $\Pi $ is the Szegö 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 the degeneracy of this completely integrable structure. We also classify the traveling waves for this system.
English

Nonlinear Schrödinger equations – Integrable Hamiltonian systems – Lax pairs – Hankel operators
35B15, 37K10, 47B35

Project Id ANR EDP dispersives, ANR AHPI

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