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In this article, we provide new structural results and algorithms for the Homotopy Height problem. In broad terms, this problem quantifies how much a curve on a surface needs to be stretched to sweep continuously between two positions. More…

Computational Geometry · Computer Science 2017-11-03 Erin Wolf Chambers , Arnaud de Mesmay , Tim Ophelders

We study the perfect matching lattice of a matching covered graph $G$, generated by the incidence vectors of its perfect matchings. Building on results of Lov\'asz and de Carvalho, Lucchesi, and Murty, we give a polynomial-time algorithm…

Combinatorics · Mathematics 2025-11-07 Olha Silina

In 1963, Anton Kotzig famously conjectured that $K_{n}$, the complete graph of order $n$, where $n$ is even, can be decomposed into $n-1$ perfect matchings such that every pair of these matchings forms a Hamilton cycle. The problem is still…

Combinatorics · Mathematics 2025-10-03 Stefan Glock , Amedeo Sgueglia

Ehrenborg noted that all tilings of a bipartite planar graph are encoded by its cubical matching complex and claimed that this complex is collapsible. We point out to an oversight in his proof and explain why these complexes can be the…

Combinatorics · Mathematics 2019-04-09 Duško Jojić

In this paper, we study degree conditions for the existence of large matchings in uniform hypergraphs. We prove that for integers $k,l,n$ with $k\ge 3$, $k/2<l<k$, and $n$ large, if $H$ is a $k$-uniform hypergraph on $n$ vertices and…

Combinatorics · Mathematics 2019-11-19 Hongliang Lu , Xingxing Yu , Xiaofan Yuan

In connection with commutative algebra, Bayer et al. introduced cut complexes in [Topology of cut complexes of graphs, SIAM J.\ Discrete Math., 38(2):1630-1675, 2024]. For a positive integer $k$, the $k$-cut complex of a graph $G$, denoted…

Combinatorics · Mathematics 2026-03-25 Pratiksha Chauhan , Samir Shukla

In this paper, we study the flip graph on the perfect matchings of a complete graph of even order. We investigate its combinatorial and spectral properties including connections to the signed reversal graph and we improve a previous upper…

Combinatorics · Mathematics 2021-10-20 Sebastian M. Cioabă , Gordon Royle , Zhao Kuang Tan

In this paper, we determine the homotopy type of the Morse complex and matching complex of multiple families of complexes by utilizing star cluster collapses and the Cluster Lemma. We compute the homotopy type of the Morse complex of an…

Algebraic Topology · Mathematics 2022-07-29 Connor Donovan , Nicholas A. Scoville

In his work on molecular spaces, Ivashchenko introduced the notion of an $\mathfrak{I}$-contractible transformation on a graph $G$, a family of addition/deletion operations on its vertices and edges. Chen, Yau, and Yeh used these operations…

Combinatorics · Mathematics 2025-03-06 Anton Dochtermann , Takahiro Matsushita

A simplicial complement P is a sequence of subsets of [m] and the simplicial complement P corresponds to a unique simplicial complex K with vertices in [m]. In this paper, we defined the homology of a simplicial complement…

Algebraic Topology · Mathematics 2010-11-22 Xiangjun Wang , Qibing Zheng

The fractional perfect b-matching polytope of an undirected graph G is the polytope of all assignments of nonnegative real numbers to the edges of G such that the sum of the numbers over all edges incident to any vertex v is a prescribed…

Combinatorics · Mathematics 2013-01-31 Roger E. Behrend

The perfect matching polytope, i.e. the convex hull of (incidence vectors of) perfect matchings of a graph is used in many combinatorial algorithms. Kotzig, Lov\'asz and Plummer developed a decomposition theory for graphs with perfect…

Combinatorics · Mathematics 2019-03-01 Isabel Beckenbach , Meike Hatzel , Sebastian Wiederrecht

We provide a recursive construction of an acyclic matching (also known as a gradient vector field, an equivalent notion to a discrete Morse function) on the independence complex of a graph with a simplicial vertex using given acyclic…

Combinatorics · Mathematics 2026-04-15 Sucharita Barik , Anupam Mondal , Sajal Mukherjee

In this work we study the homotopy type of multipath complexes of bidirectional path graphs and polygons, motivated by works of Vre\'cica and \v{Z}ivaljevi\'c on cycle-free chessboard complexes (that is, multipath complexes of complete…

Combinatorics · Mathematics 2026-01-12 Luigi Caputi , Carlo Collari , Jason P. Smith

Let $\mathcal{A} $ be a complexified-real arrangement of lines in $\mathbb{C}^2.$ Let $H$ be any line in $ \mathcal{A} $. Then, form a new complexified-real arrangement $ \mathcal{B}_H = \mathcal{A} \cup \mathcal{C} $ where $ \mathcal{C}…

Algebraic Topology · Mathematics 2015-07-17 Kristopher Williams

We discuss the question whether the existence of perfect matchings in a cubic graph can be seen from the spectrum of its adjacency matrix. For regular graphs in general and for three edge-disjoint perfect matchings in a cubic graph (that…

Combinatorics · Mathematics 2026-01-08 Willem H. Haemers

We show if $A$ is a finite CW-complex such that algebraic theories detect mapping spaces out of $A$, then $A$ has the homology type of a wedge of spheres of the same dimension. Furthermore, if $A$ is simply connected then $A$ has the…

Algebraic Topology · Mathematics 2019-03-15 Alyson Bittner

The topology of the matching complex for the $2\times n$ grid graph is mysterious. We describe a discrete Morse matching for a family of independence complexes $\mathrm{Ind}(\Delta_n^m)$ that include these matching complexes. Using this…

Combinatorics · Mathematics 2016-06-06 Benjamin Braun , Wesley K. Hough

The notion of graph covers (also referred to as locally bijective homomorphisms) plays an important role in topological graph theory and has found its computer science applications in models of local computation. For a fixed target graph…

Discrete Mathematics · Computer Science 2025-02-28 Jan Bok , Jiří Fiala , Nikola Jedličková , Jan Kratochvíl , Micheala Seifrtová

We describe the homotopy types of Vietoris-Rips complexes of hypercube graphs at scale $3$. We represent the vertices in the hypercube graph $Q_m$ as the collection of all subsets of $[m]=\{1, 2, \ldots, m\}$ and equip $Q_m$ with the metric…

Combinatorics · Mathematics 2023-05-15 Ziqin Feng