Representations of Hamiltonian vector fields on a torus

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Auteurs principaux: Rao, S. Eswara, Pal, Souvik
Format: Preprint
Publié: 2025
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author Rao, S. Eswara
Pal, Souvik
author_facet Rao, S. Eswara
Pal, Souvik
contents In this paper, we study the structure of Shen-Larsson modules over the Hamiltonian Lie algebra, also known as the Lie algebra of Hamiltonian vector fields on a torus. We establish necessary and sufficient conditions for the irreducibility of these modules and explicitly describe the Jordan-Hölder series of all reducible ones, which we call exceptional modules. We further prove that the submodules appearing in these composition series' exhaust all possible submodules of the exceptional modules (up to trivial modules), which in turn shows that all these modules are indecomposable, except in a solitary case. The submodules of these exceptional modules can be naturally realized as kernels and images of certain differential maps acting on tensor field modules over a symplectic torus. In particular, we provide complete answers to the questions recently posed by Pei-Sheng-Tang-Zhao [J. Inst. Math. Jussieu 2023]. Additionally, our methods yield simpler, conceptual proofs of known irreducibility results for Shen-Larsson modules over the Lie algebra of polynomial vector fields on a torus and its subalgebra of divergence-free vector fields, in a uniform manner. We conclude by classifying the submodules of Shen-Larsson modules over the polynomial vector fields on a torus, which shows that these Shen-Larsson modules are always indecomposable.
format Preprint
id arxiv_https___arxiv_org_abs_2504_14517
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Representations of Hamiltonian vector fields on a torus
Rao, S. Eswara
Pal, Souvik
Representation Theory
Primary: 17B10, 17B66, Secondary: 17B67, 17B68, 17B70
In this paper, we study the structure of Shen-Larsson modules over the Hamiltonian Lie algebra, also known as the Lie algebra of Hamiltonian vector fields on a torus. We establish necessary and sufficient conditions for the irreducibility of these modules and explicitly describe the Jordan-Hölder series of all reducible ones, which we call exceptional modules. We further prove that the submodules appearing in these composition series' exhaust all possible submodules of the exceptional modules (up to trivial modules), which in turn shows that all these modules are indecomposable, except in a solitary case. The submodules of these exceptional modules can be naturally realized as kernels and images of certain differential maps acting on tensor field modules over a symplectic torus. In particular, we provide complete answers to the questions recently posed by Pei-Sheng-Tang-Zhao [J. Inst. Math. Jussieu 2023]. Additionally, our methods yield simpler, conceptual proofs of known irreducibility results for Shen-Larsson modules over the Lie algebra of polynomial vector fields on a torus and its subalgebra of divergence-free vector fields, in a uniform manner. We conclude by classifying the submodules of Shen-Larsson modules over the polynomial vector fields on a torus, which shows that these Shen-Larsson modules are always indecomposable.
title Representations of Hamiltonian vector fields on a torus
topic Representation Theory
Primary: 17B10, 17B66, Secondary: 17B67, 17B68, 17B70
url https://arxiv.org/abs/2504.14517