v2: 18 pages, 7 figures; updated version has revised introduction and updated Section 4; v3: 21 pages, 2 new figures, added statement (b) in Proposition 1.4. and 1.7 plus extended proof; added references [1], [29], [30]; minor changes with respect to presentation
发表信息:
Discrete and Computational Geometry 37 (4) (2007), 517-543
本文描述了协多面体(即Stasheff多面体)和多面体(即Bott-Taubes多面体)的整数坐标的许多不同实现,并分别与A_n型和B_n型置换面体进行了比较。坐标是由一个算法获得的,该算法分别使用A_n或B_n型的有向Coxeter图作为唯一输入,并专门用于J. L. Loday对A_n的某个方向.所描述的实现具有作为正常扇的A型和B型寒武纪扇。这解决了N的一个猜想。为这些类型的寒武纪球迷阅读。
英文摘要:
We describe many different realizations with integer coordinates for the associahedron (i.e. the Stasheff polytope) and for the cyclohedron (i.e. the Bott-Taubes polytope) and compare them to the permutahedron of type A_n and B_n respectively.
The coordinates are obtained by an algorithm which uses an oriented Coxeter graph of type A_n or B_n respectively as only input and which specialises to a procedure presented by J.-L. Loday for a certain orientation of A_n. The described realizations have cambrian fans of type A and B as normal fans. This settles a conjecture of N. Reading for cambrian fans of these types.
A classic problem connecting algebraic and geometric combinatorics is the realization problem: given a poset, determine whether there exists a polytope whose face lattice is the poset. In 1990s, Kapranov defined a poset as a hybrid between the face poset of a permutohedron and that of an associahedron, and he asked whether this poset is realizable. Shortly after his question was posed, Reiner and Ziegler provided a realization. Based on our previous work on the nested braid fan, we provide in this paper a different realization of Kapranov's poset by constructing the vertex set and the normal f…
The second author introduced 2-associahedra as a tool for investigating functoriality properties of Fukaya categories, and he conjectured that they could be realized as face posets of convex polytopes. We introduce a family of posets called categorical $n$-associahedra, which naturally extend the second author's 2-associahedra and the classical associahedra. Categorical $n$-associahedra give a combinatorial model for the poset of strata of a compactified real moduli space of a tree arrangement of affine coordinate subspaces. We construct a family of complete polyhedral fans, called velocity fa…