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A natural problem in combinatorial rigidity theory concerns the determination of the rigidity or flexibility of bar-joint frameworks in $\mathbb{R}^d$ that admit some non-trivial symmetry. When $d=2$ there is a large literature on this…

Combinatorics · Mathematics 2025-09-30 Sean Dewar , Georg Grasegger , Eleftherios Kastis , Anthony Nixon

We study set systems formed by neighborhoods in graphs of bounded twin-width. We start by proving that such graphs have linear neighborhood complexity, in analogy to previous results concerning graphs from classes with bounded expansion and…

Logic in Computer Science · Computer Science 2023-04-27 Wojciech Przybyszewski

Simplicial complexes are a popular tool used to model higher-order interactions between elements of complex social and biological systems. In this paper, we study some combinatorial aspects of a class of simplicial complexes created by a…

Combinatorics · Mathematics 2023-05-17 Zixuan Xie , Yucheng Wang , Wanyue Xu , Liwang Zhu , Wei Li , Zhongzhi Zhang

This paper establishes new eigenvalue bounds for combinatorial Laplacians of simplicial complexes, extending previous results for flag complexes by Lew (2024) and general complexes by Shukla and Yogeshwaran (2020). Using elementary…

Combinatorics · Mathematics 2025-10-30 Xiongfeng Zhan , Xueyi Huang , Jin-Xin Zhou

We propose a generalization of the concept of a Ribbon graph suitable to provide combinatorial models for marked surfaces equipped with a G-structure. Our main insight is that the necessary combinatorics is neatly captured in the concept of…

Algebraic Topology · Mathematics 2021-06-01 Tobias Dyckerhoff , Mikhail Kapranov

Inspired by notorious combinatorial optimization problems on graphs, in this paper we consider a series of related problems defined using a metric space and topology determined by a graph. Particularly, we present the Independent Set,…

Combinatorics · Mathematics 2025-07-30 Alexander Grigoriev , Katherine Faulkner

In graph theory there are intimate connections between the expansion properties of a graph and the spectrum of its Laplacian. In this paper we define a notion of combinatorial expansion for simplicial complexes of general dimension, and…

Combinatorics · Mathematics 2016-07-12 Ori Parzanchevski , Ron Rosenthal , Ran J. Tessler

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

Simplicial complexes are extensively studied in the field of algebraic topology. They have gained attention in recent time due to their applications in fields like theoretical distributed computing and simplicial neural networks. Graphs are…

Discrete Mathematics · Computer Science 2025-12-16 Sukrit Chakraborty , Prasanta Choudhury , Arindam Mukherjee

This survey concerns regular graphs that are extremal with respect to the number of independent sets, and more generally, graph homomorphisms. More precisely, in the family of of $d$-regular graphs, which graph $G$ maximizes/minimizes the…

Combinatorics · Mathematics 2017-11-03 Yufei Zhao

In recent work, the authors developed a simple method of constructing topological spaces from certain well-behaved partially ordered sets -- those coming from sequences of relations between finite sets. This method associates a given poset…

General Topology · Mathematics 2025-09-11 Adam Bartoš , Tristan Bice , Alessandro Vignati

There has been much recent interest in random graphs sampled uniformly from the n-vertex graphs in a suitable minor-closed class, such as the class of all planar graphs. Here we use combinatorial and probabilistic methods to investigate a…

Combinatorics · Mathematics 2012-10-10 Colin McDiarmid

Interval graphs and interval orders are deeply linked. In fact, edges of an interval graphs represent the incomparability relation of an interval order, and in general, of different interval orders. The question about the conditions under…

Combinatorics · Mathematics 2023-01-03 Marta Fiori-Carones , Alberto Marcone

This survey describes some useful properties of the local homology of abstract simplicial complexes. Although the existing literature on local homology is somewhat dispersed, it is largely dedicated to the study of manifolds, submanifolds,…

The theory of $k$-regular graphs is closely related to group theory. Every $k$-regular, bipartite graph is a Schreier graph with respect to some group $G$, a set of generators $S$ (depending only on $k$) and a subgroup $H$. The goal of this…

Combinatorics · Mathematics 2016-07-27 Alexander Lubotzky , Zur Luria , Ron Rosenthal

Multiple interval graphs are a well-known generalization of interval graphs introduced in the 1970s to deal with situations arising naturally in scheduling and allocation. A $d$-interval is the union of $d$ intervals on the real line, and a…

Computational Complexity · Computer Science 2023-09-22 Virginia Ardévol Martínez , Romeo Rizzi , Florian Sikora , Stéphane Vialette

Hypergraphs, as a generalization of simplicial complexes, have long been a subject of interest in their geometric interpretation. The subdivision of simplicial complexes can, to some extent, provide insights into the geometry of simplicial…

Algebraic Topology · Mathematics 2023-11-17 Jian Liu , Ran Liu , Jie Wu

Graph-based signal processing techniques have become essential for handling data in non-Euclidean spaces. However, there is a growing awareness that these graph models might need to be expanded into `higher-order' domains to effectively…

Machine Learning · Computer Science 2024-04-15 Mustafa Hajij , Ghada Zamzmi , Theodore Papamarkou , Aldo Guzmán-Sáenz , Tolga Birdal , Michael T. Schaub

An interval graph is proper iff it has a representation in which no interval contains another. Fred Roberts characterized the proper interval graphs as those containing no induced star $K_{1,3}$. Proskurowski and Telle have studied…

Combinatorics · Mathematics 2011-10-03 Jeffrey Beyerl , Robert E. Jamison

Given an arbitrary hypergraph $\mathcal{H}$, we may glue to $\mathcal{H}$ a family of hypergraphs to get a new hypergraph $\mathcal{H}'$ having $\mathcal{H}$ as an induced subhypergraph. In this paper, we introduce three gluing techniques…

Commutative Algebra · Mathematics 2021-10-28 Mohammad Farrokhi Derakhshandeh Ghouchan , Alireza Shamsian , Ali Akbar Yazdan Pour