Lattice congruences, fans and Hopf algebras

JOURNAL OF COMBINATORIAL THEORY SERIES A

卷:110

Article

Reading, N

关键词: Coexter group;    fan poset;    hyperplane arrangement;    Malvenuto-Reutenauer Hopf algebra;    pattern avoidance;    permutohedron;    poset of regions;    weak order;   

DOI  :  10.1016/j.jcta.2004.11.001

来源: Elsevier

【 摘 要 】

We give a unified explanation of the geometric and algebraic properties of two well-known maps, one from permutations to triangulations, and another from permutations to subsets. Furthermore we give a broad generalization of the maps. Specifically, for any lattice congruence of the weak order on a Coxeter group we construct a complete fan of convex cones with strong properties relative to the corresponding lattice quotient of the weak order. We show that if a family of lattice congruences on the symmetric groups satisfies certain compatibility conditions then the family defines a sub Hopf algebra of the Malvenuto-Reutenauer Hopf algebra of permutations. Such a sub Hopf algebra has a basis which is described by a type of pattern avoidance. Applying these results, we build the Malvenuto-Reutenauer algebra as the limit of an infinite sequence of smaller algebras, where the second algebra in the sequence is the Hopf algebra of non-commutative symmetric functions. We also associate both a fan and a Hopf algebra to a set of permutations which appears to be equinumerous with the Baxter permutations. (c) 2004 Elsevier Inc. All rights reserved.

【 授权许可】

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