Duality of Hamiltonian and Lagrangian formulations for integrable systems

Fuente: arXiv
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Autores principales: Vergallo, Pierandrea, Vermeeren, Mats
Formato: Preprint
Publicado: 2026
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author Vergallo, Pierandrea
Vermeeren, Mats
author_facet Vergallo, Pierandrea
Vermeeren, Mats
contents We introduce the concept of Hamiltonian potential variables to map Hamiltonian operators into symplectic operators in a dual space. This generalises the classical trick of switching to a potential variable to obtain a Lagrangian density for the Korteweg-de Vries (KdV) equation. Building on this concept, we present the Lagrangian structure for bi-Hamiltonian systems, discuss the Lenard scheme in the symplectic formalisms, and apply this to construct pairs of Lagrangian multiforms. We discuss the key model of the KdV equation and some dispersionless limits of it. We present a pair of Lagrangian multiforms for these equations, one of which is new. We also consider the examples of polytropic gas dynamics and the constant astigmatism equation, for which no Lagrangian multiforms were previously known.
format Preprint
id arxiv_https___arxiv_org_abs_2604_19655
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Duality of Hamiltonian and Lagrangian formulations for integrable systems
Vergallo, Pierandrea
Vermeeren, Mats
Exactly Solvable and Integrable Systems
We introduce the concept of Hamiltonian potential variables to map Hamiltonian operators into symplectic operators in a dual space. This generalises the classical trick of switching to a potential variable to obtain a Lagrangian density for the Korteweg-de Vries (KdV) equation. Building on this concept, we present the Lagrangian structure for bi-Hamiltonian systems, discuss the Lenard scheme in the symplectic formalisms, and apply this to construct pairs of Lagrangian multiforms. We discuss the key model of the KdV equation and some dispersionless limits of it. We present a pair of Lagrangian multiforms for these equations, one of which is new. We also consider the examples of polytropic gas dynamics and the constant astigmatism equation, for which no Lagrangian multiforms were previously known.
title Duality of Hamiltonian and Lagrangian formulations for integrable systems
topic Exactly Solvable and Integrable Systems
url https://arxiv.org/abs/2604.19655