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arXiv · 2407.04539

Nijenhuis geometry of parallel tensors

Andrzej Derdzinski·Paolo Piccione·Ivo Terek
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Abstract

A tensor -- meaning here a tensor field $\Theta$ of any type $(p,q)$ on a manifold -- may be called integrable if it is parallel relative to some torsion-free connection. We provide analytical and geometric characterizations of integrability for differential $q$-forms, $q=0,1,2,n-1,n$ (in dimension $n$), vectors, bivectors, symmetric $(2,0)$ and $(0,2)$ tensors, as well as complex-diagonalizable and nilpotent tensors of type $(1,1)$. In most cases, integrability is equivalent to algebraic constancy of $\Theta$ coupled with the vanishing of one or more suitably defined Nijenhuis-type tensors, depending on $\Theta$ via a quasilinear first-order differential operator. For $(p,q)=(1,1)$, they include the ordinary Nijenhuis tensor.

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Andrzej Derdzinski, Paolo Piccione, Ivo Terek. 2024-07-05. Nijenhuis geometry of parallel tensors. https://doi.org/10.1007/s10231-024-01531-2

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