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The problem of determining extremal hypergraphs containing at most r isomorphic copies of some element of a given hypergraph family was first studied by Boros et al. in 2001. There are not many hypergraph families for which exact results…

Combinatorics · Mathematics 2007-12-18 Yeow Meng Chee , Alan C. H. Ling

We study the Seifert surfaces of a link by relating the embeddings of graphs by using induced graphs. As applications, we prove that every link $L$ is the boundary of an oriented surface which is obtained from a graph embedding of a…

Geometric Topology · Mathematics 2014-09-11 Dongseok Kim

This paper investigates the asymptotic nature of graph spectra when some edges of a graph are subdivided sufficiently many times. In the special case where all edges of a graph are subdivided, we find the exact limits of the $k$-th largest…

Combinatorics · Mathematics 2023-03-21 Hitesh Kumar , Bojan Mohar , Shivaramakrishna Pragada , Hanmeng Zhan

A bipartite graph $G=(V,E)$ with $V=V_1\cup V_2$ is biregular if all the vertices of a stable set $V_i$ have the same degree $r_i$ for $i=1,2$. In this paper, we give an improved new Moore bound for an infinite family of such graphs with…

Combinatorics · Mathematics 2021-03-23 Gabriela Araujo-Pardo , Cristina Dalfó , Miguel Ángel Fiol , Nacho López

An interval graph has interval count $\ell$ if it has an interval model, where among every $\ell+1$ intervals there are two that have the same length. Maximum Cut on interval graphs has been found to be NP-complete recently by Adhikary et…

Computational Complexity · Computer Science 2024-04-25 Alexey Barsukov , Bodhayan Roy

Let $G$ be a simple graph with $2n$ vertices and a perfect matching. We denote by $f(G)$ and $F(G)$ the minimum and maximum forcing number of $G$, respectively. Hetyei obtained that the maximum number of edges of graphs $G$ with a unique…

Combinatorics · Mathematics 2022-11-23 Qianqian Liu , Heping Zhang

In this paper, we provide an method to obtain the lower bound on the number of the distinct maximum genus embedding of the complete bipartite graph Kn;n (n be an odd number), which, in some sense, improves the results of S. Stahl and H.…

Combinatorics · Mathematics 2012-03-06 Guanghua Dong , Han Ren , Ning Wang , Yuanqiu Huang

We study the minimum number of maximum matchings in a bipartite multigraph G with parts $X$ and $Y$ under various conditions, refining the well-known lower bound due to M. Hall. When $|X|=n$, every vertex in $X$ has degree at least $k$, and…

Combinatorics · Mathematics 2022-11-21 Alexandr V. Kostochka , Douglas B. West , Zimu Xiang

We consider the problem of finding all allowed edges in a bipartite graph $G=(V,E)$, i.e., all edges that are included in some maximum matching. We show that given any maximum matching in the graph, it is possible to perform this…

Discrete Mathematics · Computer Science 2011-07-26 Tamir Tassa

A well-known conjecture by Erd\H{o}s states that every triangle-free graph on $n$ vertices can be made bipartite by removing at most $n^2/25$ edges. This conjecture was known for graphs with edge density at least $0.4$ and edge density at…

Combinatorics · Mathematics 2021-03-29 József Balogh , Felix Christian Clemen , Bernard Lidický

We focus in this paper on edge ideals associated to bipartite graphs and give a combinatorial characterization of those having regularity 3. When the regularity is strictly bigger than 3, we determine the first step $i$ in the minimal…

Commutative Algebra · Mathematics 2012-07-25 Oscar Fernández-Ramos , Philippe Gimenez

We consider the bipartite version of the degree/diameter problem, namely, given natural numbers {\Delta} \geq 2 and D \geq 2, find the maximum number Nb({\Delta},D) of vertices in a bipartite graph of maximum degree {\Delta} and diameter D.…

Combinatorics · Mathematics 2014-05-06 Ramiro Feria-Purón , Guillermo Pineda-Villavicencio

For a given graph $F$, the $F$-saturation number of a graph $G$, denoted by $ {sat}(G, F)$, is the minimum number of edges in an edge-maximal $F$-free subgraph of $G$. In 2017, Kor\'andi and Sudakov determined $ {sat}({G}(n, p), K_r)$…

Combinatorics · Mathematics 2023-04-18 Meysam Miralaei , Ali Mohammadian , Behruz Tayfeh-Rezaie , Maksim Zhukovskii

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

We study the problem of embedding bipartite graphs in Ahlfors-David regular sets of large dimension using results from extremal graph theory. Our main theorem states that any graph satisfying a power-improving bound on the extremal number…

Classical Analysis and ODEs · Mathematics 2026-04-03 Alex McDonald

A connected graph, on four or more vertices, is matching covered (aka 1-extendable) if every edge is present in some perfect matching. An ear decomposition theorem exists for bipartite matching covered graphs due to Hetyei. From the results…

Combinatorics · Mathematics 2026-05-21 Amit Kumar Mallik , Ajit A. Diwan , Nishad Kothari

Mixed graphs can be seen as digraphs that have both arcs and edges (or digons, that is, two opposite arcs). In this paper, we consider the case where such graphs are bipartite. As main results, we show that in this context the Moore-like…

Combinatorics · Mathematics 2016-11-08 C. Dalfó , M. A. Fiol , N. López

We study minimal free resolutions of edge ideals of bipartite graphs. We associate a directed graph to a bipartite graph whose edge ideal is unmixed, and give expressions for the regularity and the depth of the edge ideal in terms of…

Commutative Algebra · Mathematics 2012-12-04 Manoj Kummini

In this paper, we present two sharp upper bounds for the spectral radius of (bipartite) graphs with forbidden a star forest and characterize all extremal graphs. Moreover, the minimum least eigenvalue of the adjacency matrix of graph with…

Combinatorics · Mathematics 2021-02-23 Ming-Zhu Chen , A-Ming Liu , Xiao-Dong Zhang

In 2009, Kong, Wang, and Lee began work on the problem of finding the edge-balanced index sets of complete bipartite graphs $K_{m,n}$ by solving the cases where $n=1$, $2$, $3$, $4$, and $5$, and also the case where $m=n$. In an article…

Combinatorics · Mathematics 2014-05-08 Hung Hua , Christopher Raridan
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