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    A bijection between noncrossing and nonnesting partitions of types A and B

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    The total number of noncrossing partitions of type Ψ\Psi is the nnth Catalan number 1n+1(2nn)\frac{1}{n+1}\binom{2n}{n} when Ψ=An−1\Psi=A_{n-1}, and the binomial (2nn)\binom{2n}{n} when Ψ=Bn\Psi=B_n, and these numbers coincide with the correspondent number of nonnesting partitions. For type A, there are several bijective proofs of this equality, being the intuitive map that locally converts each crossing to a nesting one of them. In this paper we present a bijection between nonnesting and noncrossing partitions of types A and B that generalizes the type A bijection that locally converts each crossing to a nesting.Comment: 11 pages, 11 figures. Inverse map described. Minor changes to correct typos and clarify conten
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