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A simple graph is triangular if every edge is contained in a triangle. A sequence of integers is graphical if it is the degree sequence of a simple graph. Egan and Nikolayevsky recently conjectured that every graphical sequence whose terms…

Combinatorics · Mathematics 2024-09-06 John Talbot , Jun Yan

We classify which complete multipartite graphs are intrinsically chiral.

Geometric Topology · Mathematics 2013-03-22 Erica Flapan , Will Fletcher

Unitary graphs are arc-transitive graphs with vertices the flags of Hermitian unitals and edges defined by certain elements of the underlying finite fields. They played a significant role in a recent classification of a class of…

Combinatorics · Mathematics 2015-03-25 Sanming Zhou

Here we present certificates for 5 classes of 6-edged multigraphs whose symmetrized graph monomials may be represented as sum of squares, but not as linear combinations of partition square graphs. This is a complement to the results…

Algebraic Geometry · Mathematics 2012-02-03 Per Alexandersson

Motivated by recent extensive studies on Wenger graphs, we introduce a new infinite class of bipartite graphs of the similar type, called linearized Wenger graphs. The spectrum, diameter and girth of these linearized Wenger graphs are…

Combinatorics · Mathematics 2014-12-02 Xiwang Cao , Mei Lu , Daqing Wan , Li-Ping Wang , Qiang Wang

In this note we give a combinatorial characterization of all the unmixed bipartite graphs.

Combinatorics · Mathematics 2011-04-05 Rafael H. Villarreal

In this study, the explicit expressions for F-index and coindex of derived graphs such as a line graph, subdivision graph, vertex-semitotal graph, edge-semitotal graph, total graph and paraline graph (line graph of the subdivision graph)…

Discrete Mathematics · Computer Science 2016-10-10 Nilanjan De

We classify all normal edge ideals of edge-weighted graphs.

Commutative Algebra · Mathematics 2024-07-24 Thanh Vu , Guangjun Zhu

We prove that every $n$-vertex 4-uniform hypergraph with minimum codegree at least $\lfloor n/4 \rfloor$ has a spanning tight component. This is tight, and it settles the 4-uniform case of a conjecture of Illingworth, Lang, M\"uyesser,…

Combinatorics · Mathematics 2026-02-27 Francesco Di Braccio , Brian Hearn , Joanna Lada , Mihir Neve , Lu-Ming Zhang

For every positive integer $n$, we find a complete classification for planar graphs according to the collection of numbers of common neighbours for every $n$-tuple of distinct vertices. Our results expand the literature on planar graphical…

Combinatorics · Mathematics 2025-11-25 Riccardo W. Maffucci

We give a classification of all connected quartic graphs which are (infinity) curvature sharp in all vertices with respect to Bakry-\'Emery curvature. The result is based on a computer classification by F. Gurr and L. Watson May and a…

Combinatorics · Mathematics 2019-02-28 David Cushing , Supanat Kamtue , Norbert Peyerimhoff , Leyna Watson May

A directed hypergraph (dihypergraph) consists of a set of vertices and a set of hyperarcs, where each hyperarc is partitioned into a head and a tail. Directed hypergraphs are useful in many applications, including the study of chemical…

Combinatorics · Mathematics 2026-04-14 Catherine Greenhill , Tamás Makai

Hierarchical graph clustering is a common technique to reveal the multi-scale structure of complex networks. We propose a novel metric for assessing the quality of a hierarchical clustering. This metric reflects the ability to reconstruct…

Social and Information Networks · Computer Science 2018-07-16 Thomas Bonald , Bertrand Charpentier

A perfect matching in a 4-uniform hypergraph is a subset of $\lfloor\frac{n}{4}\rfloor$ disjoint edges. We prove that if $H$ is a sufficiently large 4-uniform hypergraph on $n=4k$ vertices such that every vertex belongs to more than…

Discrete Mathematics · Computer Science 2015-03-18 Imdadullah Khan

We prove an asymptotic formula for the number of $k$-uniform hypergraphs with a given degree sequence, for a wide range of parameters. In particular, we find a formula that is asymptotically equal to the number of $d$-regular $k$-uniform…

Combinatorics · Mathematics 2022-02-01 Nina Kamčev , Anita Liebenau , Nick Wormald

An oriented hypergraph is an oriented incidence structure that extends the concept of a signed graph. We introduce hypergraphic structures and techniques central to the extension of the circuit classification of signed graphs to oriented…

Combinatorics · Mathematics 2016-01-21 Lucas J. Rusnak

In this paper, we prove that for any $k\ge 3$, there exist infinitely many minimal asymmetric $k$-uniform hypergraphs. This is in a striking contrast to $k=2$, where it has been proved recently that there are exactly $18$ minimal asymmetric…

Combinatorics · Mathematics 2023-04-03 Yiting Jiang , Jaroslav Nešetřil

We prove that the notion of a derived voltage graph comes from an adjunction between the category of voltage graphs and a category of group labeled graphs.

Combinatorics · Mathematics 2024-11-20 Gejza Jenča

A sequence $\sigma$ of $p$ non-negative integers is unigraphic if it is the degree sequence of exactly one graph, up to isomorphism. A polyhedral graph is a $3$-connected, planar graph. We investigate which sequences are unigraphic with…

Combinatorics · Mathematics 2023-01-20 Jim Delitroz , Riccardo W. Maffucci

Undirected co-graphs are those graphs which can be generated from the single vertex graph by disjoint union and join operations. Co-graphs are exactly the P_4-free graphs (where P_4 denotes the path on 4 vertices). Co-graphs itself and…

Discrete Mathematics · Computer Science 2020-10-23 Frank Gurski , Dominique Komander , Carolin Rehs