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Consider the poset of partitions of {1,...(n-1)k+1} with block sizes congruent to 1 modulo k. We prove that its order complex is a subdivision of the complex of k-trees, thereby answering a question posed by Feichtner. The result is…

Combinatorics · Mathematics 2007-05-23 Emanuele Delucchi

We study an abstract notion of tree structure which lies at the common core of various tree-like discrete structures commonly used in combinatorics: trees in graphs, order trees, nested subsets of a set, tree-decompositions of graphs and…

Combinatorics · Mathematics 2017-02-28 Reinhard Diestel

For stacked simplicial complexes, (special subclasses of such are: trees, triangulations of polygons, stacked polytopes), we give an explicit bijection between partitions of facets (for trees: edges), and partitions of vertices into…

Combinatorics · Mathematics 2024-01-17 Gunnar Fløystad

We demonstrate the versatility of the tangle-tree duality theorem for abstract separation systems by using it to prove tree-of-tangles theorems. This approach allows us to strengthen some of the existing tree-of-tangles theorems by bounding…

Combinatorics · Mathematics 2025-05-20 Christian Elbracht , Jay Lilian Kneip , Maximilian Teegen

Given a finite group G and a natural number n, we study the structure of the complex of nested sets of the associated Dowling lattice Q(G) and of its subposet of the G-symmetric partitions Q_G which was recently introduced by Hultman…

Combinatorics · Mathematics 2007-05-23 Emanuele Delucchi

The tree complex is a simplicial complex defined in recent work of Belk, Lanier, Margalit, and Winarski with natural applications to mapping class groups and complex dynamics. In this article, we connect this setting with the study of…

Combinatorics · Mathematics 2024-09-17 Michael Dougherty

Trees are partial orderings where every element has a linearly ordered set of smaller elements. We define and study several natural notions of completeness of trees, extending Dedekind completeness of linear orders and Dedekind-MacNeille…

Combinatorics · Mathematics 2023-01-18 Valentin Goranko , Ruaan Kellerman , Alberto Zanardo

We construct a homotopy initial functor from the partition complex of a finite set $A$ to a category of trees with leaves labelled by $A$. As an application, this provides an equivalence between different bar constructions of an operad. In…

Algebraic Topology · Mathematics 2021-12-16 Gijs Heuts , Ieke Moerdijk

The basic result of this note is a statement about the existence of families of partitions of the set of natural numbers with some favourable properties, the n-optimal matrices of partitions. We use this to improve a decomposition result…

Logic · Mathematics 2010-05-28 Gido Scharfenberger-Fabian

Much information about a graph can be obtained by studying its spanning trees. On the other hand, a graph can be regarded as a 1-dimensional cell complex, raising the question of developing a theory of trees in higher dimension. As observed…

Combinatorics · Mathematics 2015-06-24 Art M. Duval , Caroline J. Klivans , Jeremy L. Martin

Trees are partial orders in which every element has a linearly ordered set of predecessors. Here we initiate the exploration of the structural theory of trees with the study of different notions of \emph{branching in trees} and of…

Combinatorics · Mathematics 2023-01-18 Valentin Goranko , Ruaan Kellerman , Alberto Zanardo

We consider the rooted trees which not have isomorphic representation and introduce a conception of complexity a natural number also. The connection between quantity such trees with $n$ edges and a complexity of natural number $n$ is…

Combinatorics · Mathematics 2012-05-03 B. S. Kochkarev

We introduce two definitions of $G$-equivariant partitions of a finite $G$-set, both of which yield $G$-equivariant partition complexes. By considering suitable notions of equivariant trees, we show that $G$-equivariant partitions and…

Algebraic Topology · Mathematics 2026-02-04 Julia E. Bergner , Peter Bonventre , Maxine E. Calle , David Chan , Maru Sarazola

We generalize some homotopy calculation techniques such as splittings and matching trees that are introduced for the computations in the case of the independence complexes of graphs to arbitrary simplicial complexes, and exemplify their…

Combinatorics · Mathematics 2015-01-28 Demet Taylan

There are two natural simplicial complexes associated to the noncrossing partition lattice: the order complex of the full lattice and the order complex of the lattice with its bounding elements removed. The latter is a complex that we call…

Combinatorics · Mathematics 2017-07-21 Michael Dougherty , Jon McCammond

In 1983 Kalai proved an incredible generalisation of Cayley's formula for the number of trees on a labelled vertex set to a formula for a class of $r$-dimensional simplicial complexes. These simplicial complexes generalise trees by means of…

Combinatorics · Mathematics 2019-12-05 Lewis Mead

In this article, we discuss the vertex decomposability of three well-studied simplicial complexes associated to forests. In particular, we show that the bounded degree complex of a forest and the complex of directed trees of a multidiforest…

Combinatorics · Mathematics 2021-01-15 Anurag Singh

Tree sets are posets with additional structure that generalize tree-like objects in graphs, matroids, or other combinatorial structures. They are a special class of abstract separation systems. We study infinite tree sets and how they…

Combinatorics · Mathematics 2025-05-16 Jay Lilian Kneip

In this paper we present a unifying approach to study the homotopy type of several complexes arising from forests. We show that this method applies uniformly to many complexes that have been extensively studied.

Combinatorics · Mathematics 2007-05-23 M. Marietti , D. Testa

We already saw in [A1] that the space of dynamically marked rational maps can be identified to a subspace of the space of covers between trees of spheres on which there is a notion of convergence that makes it sequentially compact. In the…

Dynamical Systems · Mathematics 2017-09-15 Matthieu Arfeux
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