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An independent vertex set of a graph is a set of vertices of the graph in which no two vertices are adjacent, and a maximal independent set is one that is not a proper subset of any other independent set. In this paper we count the number…

Combinatorics · Mathematics 2017-09-13 Seungsang Oh

In this paper we consider module-composed graphs, i.e. graphs which can be defined by a sequence of one-vertex insertions v_1,...,v_n, such that the neighbourhood of vertex v_i, 2<= i<= n, forms a module (a homogeneous set) of the graph…

Data Structures and Algorithms · Computer Science 2007-07-23 Frank Gurski

This paper investigates the shellability of $r$-independence complexes $\mathcal{I}_r(G)$, a generalization of classical independence complexes introduced by Paolini and Salvetti. For a graph $G$, a subset $A \subseteq V(G)$ is…

Combinatorics · Mathematics 2025-09-24 Arka Ghosh , S Selvaraja

We study the topological persistence of the (path) configuration spaces and the (path) independence complexes for digraphs as well as their underlying graphs. We construct some canonical embeddings from the (path) independence complexes of…

Combinatorics · Mathematics 2025-09-08 Shiquan Ren

The matching complex of a graph is the simplicial complex whose vertex set is the set of edges of the graph with a face for each independent set of edges. In this paper we completely characterize the pairs (graph, matching complex) for…

Combinatorics · Mathematics 2020-03-24 Margaret Bayer , Bennet Goeckner , Marija Jelić Milutinović

A Hamiltonian path (a Hamiltonian cycle) in a graph is a path (a cycle, respectively) that traverses all of its vertices. The problems of deciding their existence in an input graph are well-known to be NP-complete, in fact, they belong to…

Discrete Mathematics · Computer Science 2025-04-02 Nikola Jedličková , Jan Kratochvíl

We introduce a method to reduce the study of the topology of a simplicial complex to that of a simpler one. We give some applications of this method to complexes arising from graphs. As a consequence, we answer some questions raised in…

Combinatorics · Mathematics 2007-05-23 Mario Marietti , Damiano Testa

The perfect matching complex of a simple graph $G$ is a simplicial complex having facets (maximal faces) as the perfect matchings of $G$. This article discusses the perfect matching complex of polygonal line tilings and the $\left(2 \times…

Combinatorics · Mathematics 2025-04-08 Himanshu Chandrakar , Anurag Singh

We study two simplicial complexes arising from a directed graph $G = (V, E)$ with two chosen vertices $s$ and $t$: the *path-free complex*, consisting of all subsets $F \subseteq E$ that contain no path from $s$ to $t$, and the…

Combinatorics · Mathematics 2025-06-12 Darij Grinberg , Lukas Katthän , Joel Brewster Lewis

A hexagonal patch is a plane graph in which inner faces have length 6, inner vertices have degree 3, and boundary vertices have degree 2 or 3. We consider the following counting problem: given a sequence of twos and threes, how many…

Discrete Mathematics · Computer Science 2009-07-15 Paul Bonsma , Felix Breuer

Recently there has been growing interest in discrete homotopies and homotopies of graphs beyond treating graphs as 1-dimensional simplicial spaces. One such type of homotopy is $\times$-homotopy. Recent work by Chih-Scull has developed a…

Combinatorics · Mathematics 2025-04-22 Keira Behal , Tien Chih

We investigate when the independence complex of $G[H]$, the lexicographical product of two graphs $G$ and $H$, is either vertex decomposable or shellable. As an application, we construct an infinite family of graphs with the property that…

Combinatorics · Mathematics 2015-05-13 Kevin N. Vander Meulen , Adam Van Tuyl

The independence gap of a graph was introduced by Ekim et al. (2018) as a measure of how far a graph is from being well-covered. It is defined as the difference between the maximum and minimum size of a maximal independent set. We…

Combinatorics · Mathematics 2018-12-14 Tınaz Ekim , Didem Gözüpek , Ademir Hujdurović , Martin Milanič

The independence polynomial of a hypergraph is the generating function for its independent (vertex) sets with respect to their cardinality. This article aims to discuss several recurrence relations for the independence polynomial using some…

Combinatorics · Mathematics 2014-06-12 Martin Trinks

A Hamiltonian path (cycle) in a graph is a path (cycle, respectively) which passes through all of its vertices. The problems of deciding the existence of a Hamiltonian cycle (path) in an input graph are well known to be NP-complete, and…

Combinatorics · Mathematics 2024-03-07 Nikola Jedličková , Jan Kratochvíl

Let $G=(V,E)$ be a graph and $n$ a positive integer. Let $I_n(G)$ be the abstract simplicial complex whose simplices are the subsets of $V$ that do not contain an independent set of size $n$ in $G$. We study the collapsibility numbers of…

Combinatorics · Mathematics 2024-10-15 Minki Kim , Alan Lew

Consider a graph on the non-singular matrices over a finite field, in which two distinct non-singular matrices are joined by an edge whenever their sum is singular. We prove an upper bound for the independence number of this graph. As a…

Combinatorics · Mathematics 2024-05-15 Bogdan Nica

Let $G$ be a graph and $r \ge 1$. A vertex subset is $r$-independent if every connected component of its induced subgraph has size at most $r$. The family of all such subsets forms a simplicial complex, the $r$-independence complex…

Combinatorics · Mathematics 2026-05-26 Rutuja Sawant

The matching complex of a simple graph $G$ is a simplicial complex consisting of the matchings on $G$. Jeli\'c Milutinovi\'c et al. studied the matching complexes of the polygonal line tilings, and they gave a lower bound for the…

Combinatorics · Mathematics 2022-06-17 Takahiro Matsushita

Finding Hamitonian Cycles in square grid graphs is a well studied and important questions. More recent work has extended these results to triangular and hexagonal grids, as well as further restricted versions. In this paper, we examine a…

Computational Complexity · Computer Science 2018-05-09 Kaiying Hou , Jayson Lynch