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Using cyclotomy, we construct a new infinite family of Neumaier graphs that includes infinitely many strongly regular graphs. Notably, this family conjecturally contains infinitely many graphs with coherent rank $6$. Our construction also…

Combinatorics · Mathematics 2025-04-17 Gary R. W. Greaves , Zhao Kuang Tan

The symmetric edge polytope of a simple graph is a lattice polytope defined as the convex hull of a subset of the type A roots corresponding to the edges of the graph. In this article we prove a sharp lower bound for the number of edges of…

Combinatorics · Mathematics 2025-12-19 Giulia Codenotti , Roberto Riccardi , Lorenzo Venturello

$Hom(G,H)$ is a polyhedral complex defined for any two undirected graphs $G$ and $H$. This construction was introduced by Lov\'asz to give lower bounds for chromatic numbers of graphs. In this paper we initiate the study of the topological…

Combinatorics · Mathematics 2007-05-23 Eric Babson , Dmitry N. Kozlov

We define term rewriting systems on the vertices and faces of nestohedra, and show that the former are confluent and terminating. While the associated posets on vertices generalize Barnard--McConville's flip order for graph-associahedra,…

Category Theory · Mathematics 2025-01-22 Pierre-Louis Curien , Guillaume Laplante-Anfossi

Vertex-stabilizers of trivalent edge-transitive graphs have been classified by Tutte, Goldschmidt and some others in several previous papers. Tetravalent half-arc-transitive graphs form an important class of tetravalent edge-transitive…

Combinatorics · Mathematics 2025-09-01 Jin-Xin Zhou

The family of graphs of reduced words of a certain subcollection of permutations in the union $\cup_{n\geq 4}\frak{S}_{n}$ of symmetic groups is investigated. The subcollection is characterised by the hook cycle type $(n-2,1,1)$ with…

Combinatorics · Mathematics 2024-06-17 Praise Adeyemo

Let $F$ be a family of pseudo-disks in the plane, and $P$ be a finite subset of $F$. Consider the hypergraph $H(P,F)$ whose vertices are the pseudo-disks in $P$ and the edges are all subsets of $P$ of the form $\{D \in P \mid D \cap S \neq…

Computational Geometry · Computer Science 2018-02-27 Boris Aronov , Anirudh Donakonda , Esther Ezra , Rom Pinchasi

In 1992, Kalai and Kleitman proved the first subexponential upper bound for the diameters of convex polyhedra. Eisenbrand et al. proved this bound holds for connected layer families, a novel approach to analyzing polytope diameters. Very…

Combinatorics · Mathematics 2014-12-19 J. Mackenzie Gallagher , Edward D. Kim

Complexes of (not) connected graphs, hypergraphs and their homology appear in the construction of knot invariants given by V. Vassiliev. In this paper we study the complexes of not $i$-connected $k$-hypergraphs on $n$ vertices. We show that…

Combinatorics · Mathematics 2016-09-07 Eric Babson , Anders Björner , Svante Linusson , John Shareshian , Volkmar Welker

We study the relationship between the vertices of an up-monotone polyhedron $R$ and those of the polytope $P$ obtained by truncating $R$ with the unit hypercube. When $R$ has binary vertices, we characterize the vertices of $P$ in terms of…

Combinatorics · Mathematics 2018-01-08 Néstor E. Aguilera , Ricardo D. Katz , Paola B. Tolomei

We investigate symmetric edge polytopes generated by Erd\H{o}s--R\'enyi random graphs in a high-dimensional regime. These objects provide a natural and largely unexplored model of random lattice polytopes, in which geometric properties are…

Combinatorics · Mathematics 2026-03-12 Torben Donzelmann , Martina Juhnke , Benedikt Rednoß , Christoph Thäle

The polytope subalgebra of deformations of a zonotope can be endowed with the structure of a module over the Tits algebra of the corresponding hyperplane arrangement. We explore this construction and find relations between statistics on…

Combinatorics · Mathematics 2025-02-14 Jose Bastidas

We construct an infinite family of 4-polytopes whose realization spaces have dimension smaller or equal to 96. This in particular settles a problem going back to Legendre and Steinitz: whether and how the dimension of the realization space…

Combinatorics · Mathematics 2014-03-20 Karim A. Adiprasito , Günter M. Ziegler

Clique-node and closed neighborhood matrices of circular interval graphs are circular matrices. The stable set polytope and the dominating set polytope on these graphs are therefore closely related to the set packing polytope and the set…

Combinatorics · Mathematics 2018-02-21 Silvia Bianchi , Graciela Nasini , Paola Tolomei , Luis Miguel Torres

Polypolyhedra are edge-transitive compounds of polyhedra. In this paper we use group theory to determine the number of distinct polypolyhedra whose symmetry group is any given finite irreducible Coxeter group. We apply this result in order…

This paper is devoted to the study of lower and upper bounds for the number of vertices of the polytope of $n\times n\times n$ stochastic tensors (i.e., triply stochastic arrays of dimension $n$). By using known results on polytopes (i.e.,…

Combinatorics · Mathematics 2017-02-15 Zhongshan Li , Fuzhen Zhang , Xiao-Dong Zhang

Given an undirected graph, the non-empty subgraph polytope is the convex hull of the characteristic vectors of pairs (F, S) where S is a non-empty subset of nodes and F is a subset of the edges with both endnodes in S. We obtain a strong…

Discrete Mathematics · Computer Science 2015-02-17 Michele Conforti , Volker Kaibel , Matthias Walter , Stefan Weltge

The associahedron is a polytope whose graph is the graph of flips on triangulations of a convex polygon. Pseudotriangulations and multitriangulations generalize triangulations in two different ways, which have been unified by Pilaud and…

Combinatorics · Mathematics 2013-10-29 Vincent Pilaud , Francisco Santos

We characterize the edges of two classes of $0/1$-polytopes. The first class corresponds to the stable set polytope of a graph $G$ and includes chain polytopes of posets, some instances of matroid independence polytopes, as well as…

Combinatorics · Mathematics 2021-10-27 Farid Aliniaeifard , Carolina Benedetti , Nantel Bergeron , Shu Xiao Li , Franco Saliola

Binary geometries have recently been introduced in particle physics in connection with stringy integrals. In this work, we study a class of simple polytopes, called \emph{pellytopes}, whose number of vertices are given by Pell's numbers. We…

Algebraic Geometry · Mathematics 2024-10-11 Lara Bossinger , Máté L. Telek , Hannah Tillmann-Morris