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The dual complex associated to a resolution of singularities generalizes the notion of a resolution graph of a surface singularity to any dimension. We show that homotopy type of the dual complex is an invariant of an isolated singularity.

Algebraic Geometry · Mathematics 2015-06-26 D. A. Stepanov

The independence equivalence class of a graph $G$ is the set of graphs that have the same independence polynomial as $G$. Beaton, Brown and Cameron (arXiv:1810.05317) found the independence equivalence classes of even cycles, and raised the…

Combinatorics · Mathematics 2022-08-16 Boon Leong Ng

A graph $G$ is $d$-distinguishable if there is a coloring of the vertices with $d$ colors so that only the trivial automorphism preserves the color classes. The smallest such $d$ is the distinguishing number, $\operatorname{Dist}(G)$. The…

Combinatorics · Mathematics 2021-02-01 Debra Boutin , Sally Cockburn , Lauren Keough , Sarah Loeb , K. E. Perry , Puck Rombach

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 consider the homotopy type of maps between symplectic surface whose graphs form symplectic submanifolds of the product. We give a purely topological model for this space in terms of maps with constrained numbers of pre-images. We use…

Symplectic Geometry · Mathematics 2007-05-23 Joseph Coffey

The enumeration of independent sets of regular graphs is of interest in statistical mechanics, as it corresponds to the solution of hard-particle models. In 2004, it was conjectured by Fendleyet al. that for some rectangular grids, with…

Combinatorics · Mathematics 2008-10-31 Mireille Bousquet-Mélou , Svante Linusson , Eran Nevo

We study the behaviour of clique complexes of graphs under the operation of taking graph powers. As an example we compute the clique complexes of powers of cycles, or, in other words, the independence complexes of circular complete graphs.

Combinatorics · Mathematics 2015-03-19 Michal Adamaszek

We investigate a notion of $\times$-homotopy of graph maps that is based on the internal hom associated to the categorical product in the category of graphs. It is shown that graph $\times$-homotopy is characterized by the topological…

Combinatorics · Mathematics 2008-07-07 Anton Dochtermann

Let $G$ be a group. The power graph of $G$ is a graph with vertex set $G$ in which two distinct elements $x,y$ are adjacent if one of them is a power of the other. We characterize all groups whose power graphs have finite independence…

Combinatorics · Mathematics 2019-10-16 P. J. Cameron , S. H. Jafari

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

For simple graphs $G$ and $H$, the Hom complex $\mathrm{Hom}(G,H)$ is a polyhedral complex whose vertices are the graph homomorphisms $G\to H$ and whose edges connect the pairs of homomorphisms which differ in a single vertex of $G$. Hom…

Combinatorics · Mathematics 2025-09-08 Soichiro Fujii , Yuni Iwamasa , Kei Kimura , Yuta Nozaki , Akira Suzuki

The general position problem for graphs was inspired by the no-three-in-line problem from discrete geometry. A set $S$ of vertices of a graph $G$ is a \emph{general position set} if no shortest path in $G$ contains three or more vertices of…

Combinatorics · Mathematics 2024-04-02 Elias John Thomas , Ullas Chandran , James Tuite , Gabriele Di Stefano

The matching complex $M(G)$ of a simple graph $G$ is the simplicial complex consisting of the matchings on $G$. The matching complex $M(G)$ is isomorphic to the independence complex of the line graph $L(G)$. Braun and Hough introduced a…

Combinatorics · Mathematics 2019-07-01 Takahiro Matsushita

A set $S$ of vertices is a determining set for a graph $G$ if every automorphism of $G$ is uniquely determined by its action on $S$. The size of a smallest determining set for $G$ is called its determining number, $Det(G)$. A graph $G$ is…

Combinatorics · Mathematics 2021-03-09 Debra Boutin , Sally Cockburn , Lauren Keough , Sarah Loeb , K. E. Perry , Puck Rombach

A flag complex can be defined as a simplicial complex whose simplices correspond to complete subgraphs of its 1-skeleton taken as a graph. In this article, by introducing the notion of s-dismantlability, we shall define the s-homotopy type…

Combinatorics · Mathematics 2019-06-04 Romain Boulet , Etienne Fieux , Bertrand Jouve

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

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

If for any $k$ the $k$-th coefficient of a polynomial I(G;x) is equal to the number of stable sets of cardinality $k$ in graph $G$, then it is called the independence polynomial of $G$ (Gutman and Harary, 1983). J. I. Brown, K. Dilcher and…

Combinatorics · Mathematics 2007-05-23 Vadim E. Levit , Eugen Mandrescu

We prove that independence complex of a bipartite circle graph is homotopy equivalent to a wedge of spheres, resolving a conjecture posed by Przytycki and Silvero. As a corollary, we obtain that extreme Khovanov spectrum,…

Geometric Topology · Mathematics 2023-03-22 Apratim Chakraborty

We show that there are polynomial-time algorithms to compute maximum independent sets in the categorical products of two cographs and two splitgraphs. The ultimate categorical independence ratio of a graph G is defined as lim_{k --> infty}…

Discrete Mathematics · Computer Science 2013-06-10 Wing-Kai Hon , Ton Kloks , Hsiang-Hsuan Liu , Sheung-Hung Poon , Yue-Li Wang