Robust (rainbow) subdivisions and simplicial cycles

I Tomon - arXiv preprint arXiv:2201.12309, 2022 - arxiv.org
We present several results in extremal graph and hypergraph theory of topological nature.
First, we show that if $\alpha> 0$ and $\ell=\Omega (\frac {1}{\alpha}\log\frac {1}{\alpha}) $ is …

Towards the Erdős-Gallai cycle decomposition conjecture

M Bucić, R Montgomery - Proceedings of the 55th Annual ACM …, 2023 - dl.acm.org
In the 1960's, Erdős and Gallai conjectured that the edges of any n-vertex graph can be
decomposed into O (n) cycles and edges. We improve upon the previous best bound of O (n …

Essentially tight bounds for rainbow cycles in proper edge-colourings

N Alon, M Bucić, L Sauermann, D Zakharov… - arXiv preprint arXiv …, 2023 - arxiv.org
An edge-coloured graph is said to be rainbow if no colour appears more than once.
Extremal problems involving rainbow objects have been a focus of much research over the …

The extremal number of cycles with all diagonals

D Bradač, A Methuku, B Sudakov - International Mathematics …, 2024 - academic.oup.com
In 1975, Erd̋s asked the following question: What is the maximum number of edges that an-
vertex graph can have without containing a cycle with all diagonals? Erd̋s observed that …

On the Turán number of the hypercube

O Janzer, B Sudakov - Forum of Mathematics, Sigma, 2024 - cambridge.org
On the Turán number of the hypercube Page 1 Forum of Mathematics, Sigma (2024), Vol. 12:e38
1–19 doi:10.1017/fms.2024.27 RESEARCH ARTICLE On the Turán number of the hypercube …

Rainbow subdivisions of cliques

T Jiang, S Letzter, A Methuku… - Random Structures & …, 2024 - Wiley Online Library
We show that for every integer m≥ 2 m ≥ 2 and large nn, every properly edge‐colored
graph on nn vertices with at least n (log n) 53 n\left (\log n\right)^ 53 edges contains a …

Sublinear expanders and their applications

S Letzter - Surveys in Combinatorics, to appear, 2024 - arxiv.org
In this survey we aim to give a comprehensive overview of results using sublinear
expanders. The term sublinear expanders refers to a variety of definitions of expanders …

The Turán density of tight cycles in three-uniform hypergraphs

N Kamčev, S Letzter, A Pokrovskiy - International mathematics …, 2024 - academic.oup.com
The Turán density of an-uniform hypergraph, denoted, is the limit of the maximum density of
an-vertex-uniform hypergraph not containing a copy of, as. Denote by the-uniform tight cycle …

Hypergraphs with no tight cycles

S Letzter - Proceedings of the American Mathematical Society, 2023 - ams.org
We show that every $ r $-uniform hypergraph on $ n $ vertices which does not contain a tight
cycle has at most $ O (n^{r-1}(\log n)^ 5) $ edges. This is an improvement on the previously …

Rainbow Turán number of clique subdivisions

T Jiang, A Methuku, L Yepremyan - European Journal of Combinatorics, 2023 - Elsevier
We show that for any integer t≥ 2, every properly edge-coloured graph on n vertices with
more than n 1+ o (1) edges contains a rainbow subdivision of K t. Note that this bound on the …