Lagrangian multiforms on coadjoint orbits for finite-dimensional integrable systems

V Caudrelier, M Dell'Atti, AA Singh - Letters in Mathematical Physics, 2024 - Springer
Lagrangian multiforms provide a variational framework to describe integrable hierarchies.
The case of Lagrangian 1-forms covers finite-dimensional integrable systems. We use the …

On the Zakharov–Mikhailov action: Chern–Simons origin and covariant Poisson algebra of the Lax connection

V Caudrelier, M Stoppato, B Vicedo - Letters in Mathematical Physics, 2021 - Springer
We derive the 2 d Zakharov–Mikhailov action from 4 d Chern–Simons theory. This 2 d action
is known to produce as equations of motion the flatness condition of a large class of Lax …

Lagrangian multiform structure of discrete and semi-discrete KP systems

FW Nijhoff - arXiv preprint arXiv:2406.13423, 2024 - arxiv.org
A variational structure for the potential AKP system is established using the novel formalism
of a Lagrangian multiforms. The structure comprises not only the fully discrete equation on …

Lagrangian 3-form structure for the Darboux system and the KP hierarchy

FW Nijhoff - Letters in Mathematical Physics, 2023 - Springer
A Lagrangian multiform structure is established for a generalisation of the Darboux system
describing orthogonal curvilinear coordinate systems. It has been shown in the past that this …

Lagrangian multiforms for Kadomtsev–Petviashvili (KP) and the Gelfand–Dickey hierarchy

D Sleigh, FW Nijhoff, V Caudrelier - International Mathematics …, 2023 - academic.oup.com
We present, for the first time, a Lagrangian multiform for the complete Kadomtsev–
Petviashvili hierarchy—a single variational object that generates the whole hierarchy and …

Variational symmetries and Lagrangian multiforms

D Sleigh, F Nijhoff, V Caudrelier - Letters in Mathematical Physics, 2020 - Springer
By considering the closure property of a Lagrangian multiform as a conservation law, we use
Noether's theorem to show that every variational symmetry of a Lagrangian leads to a …

Classical Yang–Baxter equation, Lagrangian multiforms and ultralocal integrable hierarchies

V Caudrelier, M Stoppato, B Vicedo - Communications in Mathematical …, 2024 - Springer
We cast the classical Yang–Baxter equation (CYBE) in a variational context for the first time,
by relating it to the theory of Lagrangian multiforms, a framework designed to capture …

Multiform description of the AKNS hierarchy and classical r-matrix

V Caudrelier, M Stoppato - Journal of Physics A: Mathematical …, 2021 - iopscience.iop.org
In recent years, new properties of space-time duality in the Hamiltonian formalism of certain
integrable classical field theories have been discovered and have led to their reformulation …

[HTML][HTML] Lagrangian multiforms on Lie groups and non-commuting flows

V Caudrelier, F Nijhoff, D Sleigh… - Journal of Geometry and …, 2023 - Elsevier
We describe a variational framework for non-commuting flows, extending the theories of
Lagrangian multiforms and pluri-Lagrangian systems, which have gained prominence in …

Semi-discrete Lagrangian 2-forms and the Toda hierarchy

D Sleigh, M Vermeeren - Journal of Physics A: Mathematical and …, 2022 - iopscience.iop.org
We present a variational theory of integrable differential-difference equations (semi-discrete
integrable systems). This is an extension of the ideas known by the names' Lagrangian …