منابع مشابه
Pointed and multi-pointed partitions of type A and B
The aim of this paper is to define and study pointed and multi-pointed partition posets of type A and B (in the classification of Coxeter groups). We compute their characteristic polynomials, incidence Hopf algebras and homology groups. As a corollary, we show that some operads are Koszul over Z. Introduction For every finite Weyl group W , there exists a generalized partition poset (cf. [2]) d...
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It is shown that for any set of disjoint line segments in the plane there exists a pointed binary encompassing tree, that is, a spanning tree on the segment endpoints that contains all input segments, has maximal degree three, and such that every vertex is incident to an angle greater than π. As a consequence, it follows that every set of disjoint line segments has a bounded degree pseudo-trian...
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For a given point set S (in general position), two pointed pseudo-triangulations are compatible if their union is plane. We show that for any set S there exist two maximally disjoint compatible pointed pseudotriangulations, that is, their union is a triangulation of S. In contrast, we show that there are point sets S and pointed pseudo-triangulations T such that there exists no pointed pseudo-t...
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We show that for any set of disjoint line segments in the plane there exists a pointed binary encompassing tree T , that is, a spanning tree on the segment endpoints that contains all input segments, has maximum degree three, and every vertex v ∈ T is pointed, that is, v has an incident angle greater than π. Such a tree can be completed to a minimum pseudo-triangulation. In particular, it follo...
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Abstract. The classical Castelnuovo numbers count linear series of minimal degree and fixed dimension on a general curve, in the case when this number is finite. For pencils, that is, linear series of dimension one, the Castelnuovo numbers specialize to the better known Catalan numbers. Using the Fulton-Pragacz determinantal formula for flag bundles and combinatorial manipulations, we obtain a ...
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ژورنال
عنوان ژورنال: Nature
سال: 1996
ISSN: 0028-0836,1476-4687
DOI: 10.1038/380196b0