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It is not hard to find many complete bipartite graphs which are not determined by their spectra. We show that the graph obtained by deleting an edge from a complete bipartite graph is determined by its spectrum. We provide some graphs, each…

Combinatorics · Mathematics 2016-01-27 Chia-an Liu , Chih-wen Weng

A bipartite graph is called bipancyclic if it contains cycles of every even length from four up to the number of vertices in the graph. A theorem of Schmeichel and Mitchem states that for $n \geq 4$, every balanced bipartite graph on $2n$…

Combinatorics · Mathematics 2021-01-26 Peter Bradshaw

The celebrated dependent random choice lemma states that in a bipartite graph an average vertex (weighted by its degree) has the property that almost all small subsets $S$ in its neighborhood has common neighborhood almost as large as in…

Combinatorics · Mathematics 2022-01-27 Tao Jiang , Sean Longbrake

Sidorenko's conjecture states that the number of copies of any given bipartite graph in another graph of given density is asymptotically minimized by a random graph. The forcing conjecture further strengthens this, claiming that any…

Combinatorics · Mathematics 2024-12-18 Aldo Kiem , Olaf Parczyk , Christoph Spiegel

An $(s,t)$-matching in a bipartite graph $G=(U,V,E)$ is a subset of the edges $F$ such that each component of $G[F]$ is a tree with at most $t$ edges and each vertex in $U$ has $s$ neighbours in $G[H]$. We give sharp conditions for a…

Combinatorics · Mathematics 2016-12-07 Alexander Roberts

In this paper, we prove a tight minimum degree condition in general graphs for the existence of paths between two given endpoints, whose lengths form a long arithmetic progression with common difference one or two. This allows us to obtain…

Combinatorics · Mathematics 2021-01-27 Jun Gao , Qingyi Huo , Chun-Hung Liu , Jie Ma

Alon and Krivelevich (SIAM J. Discrete Math. 15(2): 211-227 (2002)) show that if a graph is {\epsilon}-far from bipartite, then the subgraph induced by a random subset of O(1/{\epsilon}) vertices is bipartite with high probability. We…

Data Structures and Algorithms · Computer Science 2010-11-03 Andrej Bogdanov , Fan Li

A long-standing conjecture of Berge suggests that every bridgeless cubic graph can be expressed as a union of at most five perfect matchings. This conjecture trivially holds for $3$-edge-colourable cubic graphs, but remains widely open for…

Combinatorics · Mathematics 2025-01-10 Ján Karabáš , Edita Máčajová , Roman Nedela , Martin Škoviera

We prove a far-reaching strengthening of Szemer\'edi's regularity lemma for intersection graphs of pseudo-segments. It shows that the vertex set of such a graph can be partitioned into a bounded number of parts of roughly the same size such…

Combinatorics · Mathematics 2023-12-05 Jacob Fox , Janos Pach , Andrew Suk

In a recent work on the bipartite Erd\H{o}s-R\'{e}nyi graph, Do et al. (2023) established upper bounds on the number of connected labeled bipartite graphs with a fixed surplus. We use some recent encodings of bipartite random graphs in…

Combinatorics · Mathematics 2024-11-15 David Clancy

The famous Gallai's Conjecture states that any connected graph with n vertices has a path decomposition containing at most (n+1)/2 paths. In this note, we explore graphs generated from removing edges from complete graphs. We first provide…

Combinatorics · Mathematics 2022-11-01 Hua Wang , Andrew Zhang

A graph G is perfect if for every induced subgraph H, the chromatic number of H equals the size of the largest complete subgraph of H, and G is Berge if no induced subgraph of G is an odd cycle of length at least 5 or the complement of one.…

Combinatorics · Mathematics 2007-05-23 Maria Chudnovsky , Neil Robertson , Paul Seymour , Robin Thomas

Loebl, Koml\'os and S\'os conjectured that every $n$-vertex graph $G$ with at least $n/2$ vertices of degree at least $k$ contains each tree $T$ of order $k+1$ as a subgraph. We give a sketch of a proof of the approximate version of this…

Combinatorics · Mathematics 2017-07-31 Jan Hladky , Diana Piguet , Miklos Simonovits , Maya Stein , Endre Szemeredi

It is conjectured that every edge-colored complete graph $G$ on $n$ vertices satisfying $\Delta^{mon}(G)\leq n-3k+1$ contains $k$ vertex-disjoint properly edge-colored cycles. We confirm this conjecture for $k=2$, prove several additional…

Combinatorics · Mathematics 2017-08-30 Ruonan Li , Hajo Broersma , Shenggui Zhang

The Cycle double cover (CDC) conjecture states that for every bridgeless graph $G$, there exists a family $\mathcal{F}$ of cycles such that each edge of the graph is contained in exactly two members of $\mathcal{F}$. Given an embedding of a…

Combinatorics · Mathematics 2025-11-11 Babak Ghanbari , Robert Šámal

For an odd integer $k$, let $\mathcal{C}_k = \{C_3,C_5,...,C_k\}$ denote the family of all odd cycles of length at most $k$ and let $\mathcal{C}$ denote the family of all odd cycles. Erd\H{o}s and Simonovits \cite{ESi1} conjectured that for…

Combinatorics · Mathematics 2012-10-16 Peter Allen , Peter Keevash , Benny Sudakov , Jacques Verstraete

In this paper, the concept of cyclic subsets in graph theory is introduced. An interesting theorem which relates to the collective Hamiltonicity of these cyclic subsets in graphs is also presented. This paper uses this theorem to construct…

Combinatorics · Mathematics 2014-04-08 P. Clarke

If $G$ is a bridgeless cubic graph, Fulkerson conjectured that we can find 6 perfect matchings (a{\em Fulkerson covering}) with the property that every edge of $G$ is contained in exactly two of them. A consequence of the Fulkerson…

Discrete Mathematics · Computer Science 2011-04-01 Jean-Luc Fouquet , Jean-Marie Vanherpe

We conjecture that the distribution of the edge-disjoint union of two random regular graphs on the same vertex set is asymptotically equivalent to a random regular graph of the combined degree, provided it grows as the number of vertices…

Combinatorics · Mathematics 2024-07-29 Mikhail Isaev , Brendan D. McKay , Angus Southwell , Maksim Zhukovskii

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
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