Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Generalization of Poisson-Nijenhuis Structures   We generalize Poisson-Nijenhuis structures. We prove that on a manifold
endowed with a Nijenhuis tensor and a Jacobi structure which are compatible,
there is a hierarchy of pairwise compatible Jacobi structures.
  Furthermore, we study the homogeneous Poisson-Nijenhuis structures and their
relations with Jacobi structures.

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The categories of this paper are: q-alg
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The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
7
The categories of this paper are: hep-th
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The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th
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The categories of this paper are: solv-int
3
The categories of this paper are: physics
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The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th