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By finding orthogonal representation for a family of simple connected called $\delta$-graphs it is possible to show that $\delta$-graphs satisfy delta conjecture. An extension of the argument to graphs of the form…

Combinatorics · Mathematics 2018-06-20 Pedro Díaz Navarro

There has been growing interest in studies of general random intersection graphs. In this paper, we consider a general random intersection graph $\mathbb{G}(n,\overrightarrow{a}, \overrightarrow{K_n},P_n)$ defined on a set $\mathcal{V}_n$…

Discrete Mathematics · Computer Science 2015-08-18 Jun Zhao

We investigate how to find generic and globally rigid realizations of graphs in $\mathbb{R}^d$ based on elementary geometric observations. Our arguments lead to new proofs of a combinatorial characterization of the global rigidity of graphs…

Combinatorics · Mathematics 2014-08-12 Shin-ichi Tanigawa

We show that any connected regular graph with $d+1$ distinct eigenvalues and odd-girth $2d+1$ is distance-regular, and in particular that it is a generalized odd graph.

Combinatorics · Mathematics 2012-02-13 Edwin R. van Dam , Willem H. Haemers

In this note, we provide a proof of a technical result of Erd\H{o}s and Hajnal about the existence of disjoint type graphs with no odd cycles. We also prove that this result is sharp in a certain sense.

Logic · Mathematics 2020-04-10 Chris Lambie-Hanson

A long-standing and well-known conjecture (see e.g. Caro, Discrete Math, 1994) states that every $n$-vertex graph $G$ without isolated vertices contains an induced subgraph where all vertices have an odd degree and whose order is linear in…

Combinatorics · Mathematics 2025-09-03 Jiangdong Ai , Qiwen Guo , Gregory Gutin , Yimin Hao , Anders Yeo

A graph $G=(V,E)$ is called $d$-rigid if, for a generic embedding of its vertices in $\mathbb{R}^d$, every edge-length preserving continuous motion of the vertices preserves the distances between all pairs of non-adjacent vertices as well.…

Combinatorics · Mathematics 2026-03-02 Michael Krivelevich , Alan Lew , Peleg Michaeli

The general position number ${\rm gp}(G)$ of a connected graph $G$ is the cardinality of a largest set $S$ of vertices such that no three distinct vertices from $S$ lie on a common geodesic; such sets are refereed to as gp-sets of $G$. The…

Combinatorics · Mathematics 2021-05-11 Sandi Klavžar , Balázs Patkós , Gregor Rus , Ismael G. Yero

An ordered graph is a graph with a linear ordering on its vertex set. We prove that for every positive integer $k$, there exists a constant $c_k>0$ such that any ordered graph $G$ on $n$ vertices with the property that neither $G$ nor its…

Combinatorics · Mathematics 2020-04-10 János Pach , István Tomon

A vertex subset $S$ of a graph $G$ is a general position set of $G$ if no vertex of $S$ lies on a geodesic between two other vertices of $S$. The cardinality of a largest general position set of $G$ is the general position number ${\rm…

Combinatorics · Mathematics 2019-04-17 Bijo S. Anand , Ullas Chandran S. V. , Manoj Changat , Sandi Klavžar , Elias John Thomas

Given an undirected graph $G$, let us randomly orient $G$ by tossing independent (possibly biased) coins, one for each edge of $G$. Writing $a\rightarrow b$ for the event that there exists a directed path from a vertex $a$ to a vertex $b$…

Probability · Mathematics 2017-09-07 Bhargav Narayanan

We show the following for every sufficiently connected graph $G$, any vertex subset $S$ of $G$, and given integer $k$: there are $k$ disjoint odd cycles in $G$ each containing a vertex of $S$ or there is set $X$ of at most $2k-2$ vertices…

Combinatorics · Mathematics 2016-02-17 Felix Joos

To any trivalent plane graph embedded in the sphere, Casals and Murphy associate a differential graded algebra (dg-algebra), in which the underlying graded algebra is free associative over a commutative ring. Our first result is the…

Combinatorics · Mathematics 2023-11-29 Kevin Sackel

The general position problem in graphs seeks the largest set of vertices such that no three vertices lie on a common geodesic. Its counting refinement, the general position polynomial $\psi(G)$, asks for all such possible sets. In this…

Combinatorics · Mathematics 2026-03-26 Bilal Ahmad Rather

In this paper, we prove that a graph $G$ with no $K_{s,s}$-subgraph and twin-width $d$ has $r$-admissibility and $r$-coloring numbers bounded from above by an exponential function of $r$ and that we can construct graphs achieving such a…

Combinatorics · Mathematics 2021-04-20 Jan Dreier , Jakub Gajarsky , Yiting Jiang , Patrice Ossona de Mendez , Jean-Florent Raymond

We study the interplay between the classical theory of linear series on curves, and the recent theory of linear series on graphs. We prove that every d-gonal (weighted) graph of Hurwitz type is the dual graph of a d-gonal curve. Conversely…

Algebraic Geometry · Mathematics 2013-07-23 Lucia Caporaso

An orthogonal representation of a graph is an assignment of nonzero real vectors to its vertices such that distinct non-adjacent vertices are assigned to orthogonal vectors. We prove general lower bounds on the dimension of orthogonal…

Combinatorics · Mathematics 2018-11-29 Ishay Haviv

Using a probabilistic method, we prove that $d(d+1)$-connected graphs are rigid in $\mathbb{R}^d$, a conjecture of Lov\'asz and Yemini. Then, using recent results on weakly globally linked pairs, we modify our argument to prove that…

Combinatorics · Mathematics 2023-12-05 Soma Villányi

Recently, it has been shown that a connected graph $\Gamma$ with $d+1$ distinct eigenvalues and odd-girth $2d+1$ is distance-regular. The proof of this result was based on the spectral excess theorem. In this note we present an alternative…

Combinatorics · Mathematics 2012-08-27 Edwin R. van Dam , Miquel Angel Fiol

We prove that for every nowhere dense class of graphs $\mathcal{C}$, positive integer $d$, and $\varepsilon>0$, the following holds: in every $n$-vertex graph $G$ from $\mathcal{C}$ one can find two disjoint vertex subsets $A,B\subseteq…

Combinatorics · Mathematics 2020-11-24 Marcin Briański , Piotr Micek , Michał Pilipczuk , Michał T. Seweryn