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A graph is universally $k$-edge-weightable if for every $k$-element set $Q\subset\mathbb{R}$, it admits a proper $Q$-edge weighting. The settled 1-2-3 conjecture implies that for any arithmetic progression $\{a,b,c\}$, every nice regular…

Combinatorics · Mathematics 2026-02-16 Kecai Deng

Raspaud and Wang conjectured that every triangle-free planar graph can be vertex-partitioned into an independent set and a forest. Independently, Kawarabayashi and Thomassen also remarked that this might be true, after providing another…

Combinatorics · Mathematics 2025-11-25 Guanwu Liu , Rongxing Xu

A bipartite covering of a (multi)graph $G$ is a collection of bipartite graphs, so that each edge of $G$ belongs to at least one of them. The capacity of the covering is the sum of the numbers of vertices of these bipartite graphs. In this…

Combinatorics · Mathematics 2023-08-01 Noga Alon

Graph partitioning, or the dividing of a graph into two or more parts based on certain conditions, arises naturally throughout discrete mathematics, and problems of this kind have been studied extensively. In the 1990s, Ando conjectured…

Combinatorics · Mathematics 2021-08-27 Shagnik Das , Alexey Pokrovskiy , Benny Sudakov

A graph is $k$-planar if it can be drawn in the plane such that no edge is crossed more than $k$ times. While for $k=1$, optimal $1$-planar graphs, i.e., those with $n$ vertices and exactly $4n-8$ edges, have been completely characterized,…

Computational Geometry · Computer Science 2017-03-21 Michael A. Bekos , Michael Kaufmann , Chrysanthi N. Raftopoulou

A celebrated conjecture of Sidorenko and Erd\H{o}s-Simonovits states that, for all bipartite graphs $H$, quasirandom graphs contain asymptotically the minimum number of copies of $H$ taken over all graphs with the same order and edge…

Combinatorics · Mathematics 2021-03-30 David Conlon , Joonkyung Lee

A bipartite graph is {\em pseudo 2--factor isomorphic} if all its 2--factors have the same parity of number of circuits. In \cite{ADJLS} we proved that the only essentially 4--edge-connected pseudo 2--factor isomorphic cubic bipartite graph…

Combinatorics · Mathematics 2015-01-13 M. Abreu , D. Labbate , J. Sheehan

It was recently shown \cite{STV} that satisfiability is polynomially solvable when the incidence graph is an interval bipartite graph (an interval graph turned into a bipartite graph by omitting all edges within each partite set). Here we…

Data Structures and Algorithms · Computer Science 2016-02-26 Serge Gaspers , Christos Papadimitriou , Sigve Hortemo Saether , Jan Arne Telle

A graph is "$H$-free" if it has no induced subgraph isomorphic to $H$. A conjecture of Conlon, Fox and Sudakov states that for every graph $H$, there exists $s>0$ such that in every $H$-free graph with $n>1$ vertices, either some vertex has…

Combinatorics · Mathematics 2020-12-08 Maria Chudnovsky , Jacob Fox , Alex Scott , Paul Seymour , Sophie Spirkl

An embedding of a graph in a book consists of a linear order of its vertices along the spine of the book and of an assignment of its edges to the pages of the book, so that no two edges on the same page cross. The book thickness of a graph…

Data Structures and Algorithms · Computer Science 2020-04-17 Michael A. Bekos , Michael Kaufmann , Fabian Klute , Sergey Pupyrev , Chrysanthi Raftopoulou , Torsten Ueckerdt

A graph $G$ is a non-separating planar graph if there is a drawing $D$ of $G$ on the plane such that (1) no two edges cross each other in $D$ and (2) for any cycle $C$ in $D$, any two vertices not in $C$ are on the same side of $C$ in $D$.…

Combinatorics · Mathematics 2019-07-24 Hooman R. Dehkordi , Graham Farr

For a planar graph with a given f-vector $(f_{0}, f_{1}, f_{2}),$ we introduce a cubic polynomial whose coefficients depend on the f-vector. The planar graph is said to be real if all the roots of the corresponding polynomial are real. Thus…

Combinatorics · Mathematics 2018-03-29 M. R. Emamy-K. , Bahman Kalantari , Tatiana Correa

In a book embedding of a graph G, the vertices of G are placed in order along a straight-line called spine of the book, and the edges of G are drawn on a set of half-planes, called the pages of the book, such that two edges drawn on a page…

Computational Geometry · Computer Science 2015-10-21 Md. Jawaherul Alam , Franz J. Brandenburg , Stephen G. Kobourov

We prove a sharp upper bound for the number of high degree differences in bipartite graphs: let $ (U, V, E)$ be a bipartite graph with $U=\{u_1, u_2, \dots, u_n\}$ and $V=\{v_1, v_2, \dots, v_n\}$; for $n\ge k>\frac{n}{2}$ we show that…

Combinatorics · Mathematics 2022-04-18 Stanisław Cichomski , Fedor Petrov

Biregular bipartite graphs have been proven to have similar edge distributions to random bipartite graphs and thus have nice pseudorandomness and expansion properties. Thus it is quite desirable to find a biregular bipartite spanning…

Combinatorics · Mathematics 2024-10-29 Dandan Fan , Xiaofeng Gu , Huiqiu Lin

A cubical polytope is a polytope with all its facets being combinatorially equivalent to cubes. The paper is concerned with the linkedness of the graphs of cubical polytopes. A graph with at least $2k$ vertices is \textit{$k$-linked} if,…

Combinatorics · Mathematics 2023-10-13 Hoa T. Bui , Guillermo Pineda-Villavicencio , Julien Ugon

A strong edge coloring of a graph $G$ is a proper edge coloring in which each color class is an induced matching of $G$. In 1993, Brualdi and Quinn Massey proposed a conjecture that every bipartite graph without $4$-cycles and with the…

Combinatorics · Mathematics 2013-12-09 Borut Lužar , Martina Mockovčiaková , Roman Soták , Riste Škrekovski

A balanced graph is a bipartite graph with no induced circuit of length 2 mod 4. These graphs arise in linear programming. We focus on graph-algebraic properties of balanced graphs to prove a complete classification of balanced Cayley…

Combinatorics · Mathematics 2007-07-03 Joy Morris , Pablo Spiga , Kerri Webb

We prove that there is a constant $c >0$, such that whenever $p \ge n^{-c}$, with probability tending to 1 when $n$ goes to infinity, every maximum triangle-free subgraph of the random graph $G_{n,p}$ is bipartite. This answers a question…

Probability · Mathematics 2009-08-27 Graham Brightwell , Konstantinos Panagiotou , Angelika Steger

It is well known that the complete multipartite graphs can not be determined by their adjacency spectra. But in this paper, we prove that they can be determined by their distance spectra, which confirms the conjecture proposed by Lin, Hong,…

Combinatorics · Mathematics 2013-07-24 Ya-Lei Jin , Xiao-Dong Zhang