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In this paper, we extend the recently introduced concept of partially dual ribbon graphs to graphs. We then go on to characterize partial duality of graphs in terms of bijections between edge sets of corresponding graphs. This result…

Combinatorics · Mathematics 2012-03-01 Iain Moffatt

A classical Tur\'an problem asks for the maximum possible number of edges in a graph of a given order that does not contain a particular graph $H$ as a subgraph. It is well-known that the chromatic number of $H$ is the graph parameter which…

Directions of graphs were originally introduced in the study of a cops-and-robbers kind of game, while the study of end spaces has been used to generalize classical graph-theoretical results to infinite graphs, such as Halin's…

Combinatorics · Mathematics 2025-10-21 Gustavo Boska , Matheus Duzi , Paulo Magalhães Júnior

A monitoring edge-geodetic set, or simply an MEG-set, of a graph $G$ is a vertex subset $M \subseteq V(G)$ such that given any edge $e$ of $G$, $e$ lies on every shortest $u$-$v$ path of $G$, for some $u,v \in M$. The monitoring…

Discrete Mathematics · Computer Science 2025-01-22 Florent Foucaud , Clara Marcille , Zin Mar Myint , R. B. Sandeep , Sagnik Sen , S. Taruni

Let $n\ge 1$ be an integer and $\mathbb{F}_q$ be a finite field of characteristic $p$ with $q$ elements. In this paper, it is proved that the Wenger graph $W_n(q)$ and linearized Wenger graph $L_m(q)$ are edge-girth-regular…

Combinatorics · Mathematics 2023-11-09 Fuyuan Yang , Qiang Sun , Chao Zhang

Let $F$ be a graph. We say that a hypergraph $H$ is a {\it Berge}-$F$ if there is a bijection $f : E(F) \rightarrow E(H )$ such that $e \subseteq f(e)$ for every $e \in E(F)$. Note that Berge-$F$ actually denotes a class of hypergraphs. The…

Combinatorics · Mathematics 2017-06-15 Cory Palmer , Michael Tait , Craig Timmons , Adam Zsolt Wagner

Discrete curvatures are quantities associated to the nodes and edges of a graph that reflect the local geometry around them. These curvatures have a rich mathematical theory and they have recently found success as a tool to analyze networks…

Physics and Society · Physics 2024-08-02 Michelle Roost , Karel Devriendt , Giulio Zucal , Jürgen Jost

We investigate natural Tur\'an problems for mixed graphs, generalizations of graphs where edges can be either directed or undirected. We study a natural \textit{Tur\'an density coefficient} that measures how large a fraction of directed…

Combinatorics · Mathematics 2024-03-26 Nitya Mani , Edward Yu

The extremal functions $ex_{\rightarrow}(n,F)$ and $ex_{\cir}(n,F)$ for ordered and convex geometric acyclic graphs $F$ have been extensively investigated by a number of researchers. Basic questions are to determine when…

Combinatorics · Mathematics 2019-02-04 Zoltán Füredi , Alexandr Kostochka , Dhruv Mubayi , Jacques Verstraëte

Recently, Ali et al. posed several open problems concerning extremal graphs with respect to the ABS index. These problems involve characterizing graphs that attain the maximum ABS index within specific graph classes, including: connected…

Combinatorics · Mathematics 2025-12-30 Swathi Shetty , B. R. Rakshith , Sayinath Udupa N.

We consider unavoidable chromatic patterns in $2$-colorings of the edges of the complete graph. Several such problems are explored being a junction point between Ramsey theory, extremal graph theory (Tur\'an type problems), zero-sum Ramsey…

Combinatorics · Mathematics 2019-04-09 Yair Caro , Adriana Hansberg , Amanda Montejano

An extremal graph for a given graph $H$ is a graph on $n$ vertices with maximum number of edges that does not contain $H$ as a subgraph. Let $s,t$ be integers and let $H_{s,t}$ be a graph consisting of $s$ triangles and $t$ cycles of odd…

Combinatorics · Mathematics 2016-10-05 Xinmin Hou , Yu Qiu , Boyuan Liu

The Tur\'{a}n problem asks for the largest number of edges ex$(n,H)$ in an $n$-vertex graph not containing a fixed forbidden subgraph $H$, which is one of the most important problems in extremal graph theory. However the order of magnitude…

Combinatorics · Mathematics 2024-08-06 Tao Zhang , Zixiang Xu , Gennian Ge

An ordered hypergraph is a hypergraph $G$ whose vertex set $V(G)$ is linearly ordered. We find the Tur\'an numbers for the $r$-uniform $s$-vertex tight path $P^{(r)}_s$ (with vertices in the natural order) exactly when $r\le s < 2r$ and $n$…

Combinatorics · Mathematics 2022-12-29 John P. Bright , Kevin G. Milans , Jackson Porter

For a graph $H$, the {\em extremal number} $ex(n,H)$ is the maximum number of edges in a graph of order $n$ not containing a subgraph isomorphic to $H$. Let $\delta(H)>0$ and $\Delta(H)$ denote the minimum degree and maximum degree of $H$,…

Combinatorics · Mathematics 2014-04-07 Noga Alon , Raphael Yuster

The fundamental theorem of Tur\'{a}n from Extremal Graph Theory determines the exact bound on the number of edges $t_r(n)$ in an $n$-vertex graph that does not contain a clique of size $r+1$. We establish an interesting link between…

Data Structures and Algorithms · Computer Science 2023-07-17 Fedor V. Fomin , Petr A. Golovach , Danil Sagunov , Kirill Simonov

This paper focuses on extensions of the classic Erd\H{o}s-Gallai Theorem for the set of weighted function of each edge in a graph. The weighted function of an edge $e$ of an $n$-vertex uniform hypergraph $\mathcal{H}$ is defined to a…

Combinatorics · Mathematics 2024-04-02 Kai Zhao , Xiao-Dong Zhang

This article introduces a new approach to discrete curvature based on the concept of effective resistances. We propose a curvature on the nodes and links of a graph and present the evidence for their interpretation as a curvature. Notably,…

Differential Geometry · Mathematics 2022-09-26 Karel Devriendt , Renaud Lambiotte

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

Recently, Bennett et al. introduced the vertex-induced weighted Tur\'an problem. In this paper, we consider their open Tur\'an problem under sum-edge-weight function and characterize the extremal structure of $K_{l}$-free graphs. Based on…

Combinatorics · Mathematics 2019-02-26 Zixiang Xu , Yifan Jing , Gennian Ge