Stäckel problem for non-diagonal Killing tensors: Yano-Patterson lifts, algebra of strong symmetries and quadratic in momenta integrals

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Main Authors: Bolsinov, Alexey V., Konyaev, Andrey Yu., Matveev, Vladimir S.
Format: Preprint
Published: 2025
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author Bolsinov, Alexey V.
Konyaev, Andrey Yu.
Matveev, Vladimir S.
author_facet Bolsinov, Alexey V.
Konyaev, Andrey Yu.
Matveev, Vladimir S.
contents We construct integrable Hamiltonian systems such that functionally independent Poisson commuting integrals are quadratic in the momenta. Unlike the classical Stäckel setting, we allow the associated self-adjoint $(1,1)$-tensors $K_α$ to be non-diagonalisable and have Jordan blocks and points where the Segre characteristic changes. Our construction is covariant and is based on Nijenhuis geometry: starting from a gl-regular Nijenhuis operator $L$ and its symmetry algebra, we obtain a large class of such integrable systems in a coordinate-free and signature-independent way; it is explicit once we have chosen a gl-regular Nijnhuis operator. In the diagonalisable case, our construction reproduces the Stäckel construction, and in dimension $n=2$ it recovers all known systems of this type; for $n\ge 3$ most of our systems are new. Finally, we establish applications to infinite-dimensional integrable systems of hydrodynamic type: namely, we show that for Killing $(1,1)$-tensors $ K_α$ corresponding to our example the evolutionarly PDE system of hydrodynamic type $u_t = K_α(u)u_x$ is integrable. We describe its symmetries, and use generalised reciprocal transformations to reduce it to a system with constant coefficient matrices.
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id arxiv_https___arxiv_org_abs_2512_17609
institution arXiv
publishDate 2025
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spellingShingle Stäckel problem for non-diagonal Killing tensors: Yano-Patterson lifts, algebra of strong symmetries and quadratic in momenta integrals
Bolsinov, Alexey V.
Konyaev, Andrey Yu.
Matveev, Vladimir S.
Exactly Solvable and Integrable Systems
Mathematical Physics
Differential Geometry
Dynamical Systems
We construct integrable Hamiltonian systems such that functionally independent Poisson commuting integrals are quadratic in the momenta. Unlike the classical Stäckel setting, we allow the associated self-adjoint $(1,1)$-tensors $K_α$ to be non-diagonalisable and have Jordan blocks and points where the Segre characteristic changes. Our construction is covariant and is based on Nijenhuis geometry: starting from a gl-regular Nijenhuis operator $L$ and its symmetry algebra, we obtain a large class of such integrable systems in a coordinate-free and signature-independent way; it is explicit once we have chosen a gl-regular Nijnhuis operator. In the diagonalisable case, our construction reproduces the Stäckel construction, and in dimension $n=2$ it recovers all known systems of this type; for $n\ge 3$ most of our systems are new. Finally, we establish applications to infinite-dimensional integrable systems of hydrodynamic type: namely, we show that for Killing $(1,1)$-tensors $ K_α$ corresponding to our example the evolutionarly PDE system of hydrodynamic type $u_t = K_α(u)u_x$ is integrable. We describe its symmetries, and use generalised reciprocal transformations to reduce it to a system with constant coefficient matrices.
title Stäckel problem for non-diagonal Killing tensors: Yano-Patterson lifts, algebra of strong symmetries and quadratic in momenta integrals
topic Exactly Solvable and Integrable Systems
Mathematical Physics
Differential Geometry
Dynamical Systems
url https://arxiv.org/abs/2512.17609