On the Lagrangian multiform structure of the extended lattice Boussinesq system

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Hauptverfasser: Nijhoff, F. W., Zhang, D. J.
Format: Preprint
Veröffentlicht: 2023
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author Nijhoff, F. W.
Zhang, D. J.
author_facet Nijhoff, F. W.
Zhang, D. J.
contents The lattice Boussinesq (lBSQ) equation is a member of the lattice Gel'fand-Dikii (lGD) hierarchy, introduced in \cite{NijPapCapQui1992}, which is an infinite family of integrable systems of partial difference equations labelled by an integer $N$, where $N=2$ represents the lattice Korteweg-de Vries (KdV) system, and $N=3$ the Boussinesq system. In \cite{Hiet2011} it was shown that, written as three-component system, the lBSQ system allows for extra parameters which essentially amounts to building the lattice KdV inside the lBSQ. In this paper we show that, on the level of the Lagrangian structure, this boils down to a linear combination of Lagrangians from the members of the lGD hierarchy as was established in \cite{LobbNijGD2010}. The corresponding Lagrangian multiform structure is shown to exhibit a `double zero' structure.
format Preprint
id arxiv_https___arxiv_org_abs_2312_12684
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle On the Lagrangian multiform structure of the extended lattice Boussinesq system
Nijhoff, F. W.
Zhang, D. J.
Exactly Solvable and Integrable Systems
Mathematical Physics
The lattice Boussinesq (lBSQ) equation is a member of the lattice Gel'fand-Dikii (lGD) hierarchy, introduced in \cite{NijPapCapQui1992}, which is an infinite family of integrable systems of partial difference equations labelled by an integer $N$, where $N=2$ represents the lattice Korteweg-de Vries (KdV) system, and $N=3$ the Boussinesq system. In \cite{Hiet2011} it was shown that, written as three-component system, the lBSQ system allows for extra parameters which essentially amounts to building the lattice KdV inside the lBSQ. In this paper we show that, on the level of the Lagrangian structure, this boils down to a linear combination of Lagrangians from the members of the lGD hierarchy as was established in \cite{LobbNijGD2010}. The corresponding Lagrangian multiform structure is shown to exhibit a `double zero' structure.
title On the Lagrangian multiform structure of the extended lattice Boussinesq system
topic Exactly Solvable and Integrable Systems
Mathematical Physics
url https://arxiv.org/abs/2312.12684