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The notion of forcing sets for perfect matchings was introduced by Harary, Klein, and \v{Z}ivkovi\'{c}. The application of this problem in chemistry, as well as its interesting theoretical aspects, made this subject very active. In this…

Combinatorics · Mathematics 2025-03-04 Javad B. Ebrahimi , Babak Ghanbari

A simple graph more often than not contains adjacent vertices with equal degrees. This in particular holds for all pairs of neighbours in regular graphs, while a lot such pairs can be expected e.g. in many random models. Is there a…

Combinatorics · Mathematics 2020-03-31 Jakub Przybyło

In a recent work, Keusch proved the so-called 1-2-3 Conjecture, raised by Karo\'nski, {\L}uczak, and Thomason in 2004: for every connected graph different from $K_2$, we can assign labels~$1,2,3$ to the edges so that no two adjacent…

Combinatorics · Mathematics 2025-05-08 Julien Bensmail , Beatriz Martins , Chaoliang Tang

In [{Structural properties and decomposition of linear balanced matrices}, {\it Mathematical Programming}, 55:129--168, 1992], Conforti and Rao conjectured that every balanced bipartite graph contains an edge that is not the unique chord of…

In 1984, Erd\H{o}s and Simonovits conjectured the following: given a bipartite graph $H$, there exist constants $\beta, C > 0$ such that any graph $G$ on $n$ vertices and $pn^2\geq C \mathrm{ex}(n, H)$ edges contains at least $\beta…

Combinatorics · Mathematics 2025-10-30 Zihao Jin , Sean Longbrake , Liana Yepremyan

We introduce a family of forcing notions that are helpful in showing that certain graphs do not have countable colourings of (additive) Borel class alpha. We construct graphs that are ''weakly minimal'' for such colourings.

General Topology · Mathematics 2026-04-08 Noam Greenberg , Dominique Lecomte , Dan Turetsky , Miroslav Zelen

The well-known 1-2-3 Conjecture asserts that the edges of every graph without isolated edges can be weighted with $1$, $2$ and $3$ so that adjacent vertices receive distinct weighted degrees. This is open in general, while it is known to be…

Combinatorics · Mathematics 2019-12-19 Jakub Przybyło

Let ${\mathcal G}$ be an infinite family of connected graphs and let $k$ be a positive integer. We say that $k$ is ${\it forcing}$ for ${\mathcal G}$ if for all $G \in {\mathcal G}$ but finitely many, the following holds. Any…

Combinatorics · Mathematics 2017-11-28 Yair Caro , Raphael Yuster

The zero forcing process is an iterative graph colouring process in which at each time step a coloured vertex with a single uncoloured neighbour can force this neighbour to become coloured. A zero forcing set of a graph is an initial set of…

Combinatorics · Mathematics 2018-12-18 Deepak Bal , Patrick Bennett , Sean English , Calum MacRury , Paweł Prałat

Mader first proved that high average degree forces a given graph as a minor. Often motivated by Hadwiger's Conjecture, much research has focused on the average degree required to force a complete graph as a minor. Subsequently, various…

Combinatorics · Mathematics 2017-07-18 Daniel J. Harvey , David R. Wood

We study the effect of external forcing on the saddle-node bifurcation pattern of interval maps. By replacing fixed points of unperturbed maps by invariant graphs, we obtain direct analogues to the classical result both for random forcing…

Dynamical Systems · Mathematics 2011-05-26 Vasso Anagnostopoulou , Tobias Jäger

In 1979 Frankl conjectured that in a finite non-trivial union-closed collection of sets there has to be an element that belongs to at least half the sets. We show that this is equivalent to the conjecture that in a finite non-trivial graph…

Combinatorics · Mathematics 2013-05-17 Henning Bruhn , Pierre Charbit , Oliver Schaudt , Jan Arne Telle

Karo\'nski, {\L}uczak and Thomason conjectured in 2004 that for every finite graph without isolated edge, the edges can be assigned weights from $\{1,2,3\}$ in such a way that the endvertices of each edge have different sums of incident…

Combinatorics · Mathematics 2023-04-21 Marcin Stawiski

Kang and Park recently showed that every cubic (loopless) multigraph is incidence 6-choosable [On incidence choosability of cubic graphs. \emph{arXiv}, April 2018]. Equivalently, every bipartite graph obtained by subdividing once every edge…

Combinatorics · Mathematics 2018-08-06 Petru Valicov

We enumerate factorisations of the complete bipartite graph into spanning semiregular graphs in several cases, including when the degrees of all the factors except one or two are small. The resulting asymptotic behaviour is seen to…

Combinatorics · Mathematics 2022-12-21 Mahdieh Hasheminezhad , Brendan D. McKay

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

The well-known 1-2-3 Conjecture asserts that the edges of every graph without an isolated edge can be weighted with $1$, $2$ and $3$ so that adjacent vertices receive distinct weighted degrees. This is open in general. We prove that every…

Combinatorics · Mathematics 2019-11-05 Jakub Przybyło

In 2013 Andriy V. Bondarenko showed how to construct a two-distance counterexample to Borsuk's conjecture from any strongly regular graph whose vertex set is not the union of at most $f+1$ cliques (sets of pairwise adjacent vertices) where…

Combinatorics · Mathematics 2021-06-29 Thomas Jenrich

Let $G$ be a simple graph whose vertices are partitioned into two subsets, called filled vertices and empty vertices. A vertex $v$ is said to be forced by a filled vertex $u$ if $v$ is a unique empty neighbor of $u$. If we can fill all the…

Combinatorics · Mathematics 2016-09-02 Yaroslav Shitov

This paper proves a conjecture generated by the artificial intelligence conjecturing program called \emph{TxGraffiti}. More specifically, we show that if $G$ is a connected, cubic, and claw-free graph, then $Z(G) \le \gamma(G) + 2$, where…

Combinatorics · Mathematics 2024-11-20 Randy R. Davila