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We use the polynomial method of Guth and Katz to establish stronger and {\it more efficient} regularity and density theorems for such $k$-uniform hypergraphs $H=(P,E)$, where $P$ is a finite point set in ${\mathbb R}^d$, and the edge set…

Computational Geometry · Computer Science 2024-08-15 Natan Rubin

We study the problem of graph clustering where the goal is to partition a graph into clusters, i.e. disjoint subsets of vertices, such that each cluster is well connected internally while sparsely connected to the rest of the graph. In…

Data Structures and Algorithms · Computer Science 2021-12-17 Thatchaphol Saranurak , Di Wang

In this paper we study conditions which guarantee the existence of perfect matchings and perfect fractional matchings in uniform hypergraphs. We reduce this problem to an old conjecture by Erd\H{o}s on estimating the maximum number of edges…

Combinatorics · Mathematics 2012-02-01 Noga Alon , Peter Frankl , Hao Huang , Vojtech Rodl , Andrzej Rucinski , Benny Sudakov

P. Erd\H{o}s [On extremal problems of graphs and generalized graphs, Israel Journal of Mathematics 2 (1964), 183-190] characterised those hypergraphs $F$ that have to appear in any sufficiently large hypergraph $H$ of positive density. We…

Combinatorics · Mathematics 2019-01-30 Christian Reiher , Vojtěch Rödl , Mathias Schacht

Let p(k) denote the partition function of k. For each k >= 2, we describe a list of p(k)-1 quasirandom properties that a k-uniform hypergraph can have. Our work connects previous notions on linear hypergraph quasirandomness of…

Combinatorics · Mathematics 2013-09-09 John Lenz , Dhruv Mubayi

We describe structure of quasihomomorphisms from arbitrary groups to discrete groups. We show that all quasihomomorphisms are 'constructible', i.e., are obtained via certain natural operations from homomorphisms to some groups and…

Group Theory · Mathematics 2015-07-09 Koji Fujiwara , Michael Kapovich

Chung, Graham, and Wilson proved that a graph is quasirandom if and only if there is a large gap between its first and second largest eigenvalue. Recently, the authors extended this characterization to k-uniform hypergraphs, but only for…

Combinatorics · Mathematics 2014-09-25 John Lenz , Dhruv Mubayi

A subgroup $H\leq G$ is said to be almost normal if every conjugate of $H$ is commensurable to $H$. If $H$ is almost normal, there is a well-defined quotient space $G/H$. We show that if a group $G$ has type $F_{n+1}$ and contains an almost…

Group Theory · Mathematics 2021-09-15 Alexander Margolis

A set of vertices in a graph is a Hamiltonian subset if it induces a subgraph containing a Hamiltonian cycle. Kim, Liu, Sharifzadeh and Staden proved that among all graphs with minimum degree $d$, $K_{d+1}$ minimises the number of…

Combinatorics · Mathematics 2023-01-19 Stijn Cambie , Jun Gao , Hong Liu

We show that $3$-uniform hypergraphs with the property that all vertices have a quasirandom link graph with density bigger than $1/3$ contain a clique on five vertices. This result is asymptotically best possible.

Combinatorics · Mathematics 2024-03-19 Sören Berger , Simón Piga , Christian Reiher , Vojtěch Rödl , Mathias Schacht

We study the problem of constructing a (near) uniform random proper $q$-coloring of a simple $k$-uniform hypergraph with $n$ vertices and maximum degree $\Delta$. (Proper in that no edge is mono-colored and simple in that two edges have…

Discrete Mathematics · Computer Science 2017-11-15 Michael Anastos , Alan Frieze

We consider the problem of recovering a subhypergraph based on an observed adjacency tensor corresponding to a uniform hypergraph. The uniform hypergraph is assumed to contain a subset of vertices called as subhypergraph. The edges…

Information Theory · Computer Science 2021-05-07 Mingao Yuan , Zuofeng Shang

We provide sufficient conditions for two subgroups of a hierarchically hyperbolic group to generate an amalgamated free product over their intersection. The result applies in particular to certain geometric subgroups of mapping class groups…

Group Theory · Mathematics 2026-01-07 Giorgio Mangioni

The class of quasi-chain graphs is an extension of the well-studied class of chain graphs. This latter class enjoys many nice and important properties, such as bounded clique-width, implicit representation, well-quasi-ordering by induced…

Combinatorics · Mathematics 2021-04-12 Bogdan Alecu , Aistis Atminas , Vadim Lozin , Dmitriy Malyshev

In a series of recent works, we have generalised the consistency results in the stochastic block model literature to the case of uniform and non-uniform hypergraphs. The present paper continues the same line of study, where we focus on…

Machine Learning · Computer Science 2017-05-18 Debarghya Ghoshdastidar , Ambedkar Dukkipati

For a $k$-uniform hypergraph $F$ let $\textrm{ex}(n,F)$ be the maximum number of edges of a $k$-uniform $n$-vertex hypergraph $H$ which contains no copy of $F$. Determining or estimating $\textrm{ex}(n,F)$ is a classical and central problem…

Combinatorics · Mathematics 2020-12-18 Christian Reiher

We obtain a hypergraph generalisation of the graph blow-up lemma proved by Komlos, Sarkozy and Szemeredi, showing that hypergraphs with sufficient regularity and no atypical vertices behave as if they were complete for the purpose of…

Combinatorics · Mathematics 2010-11-08 Peter Keevash

We compute a minimum degree threshold sufficient for 3-partite graphs to admit a fractional triangle decomposition. Together with recent work of Barber, K\"uhn, Lo, Osthus and Taylor, this leads to bounds for exact decompositions and in…

Combinatorics · Mathematics 2016-09-13 Flora C. Bowditch , Peter J. Dukes

We prove several results on approximate decompositions of edge-coloured quasirandom graphs into rainbow spanning structures. More precisely, we say that an edge-colouring of a graph is locally $\ell$-bounded if no vertex is incident to more…

Combinatorics · Mathematics 2019-10-01 Jaehoon Kim , Daniela Kühn , Andrey Kupavskii , Deryk Osthus

Hypergraphs, as a generalization of simplicial complexes, have long been a subject of interest in their geometric interpretation. The subdivision of simplicial complexes can, to some extent, provide insights into the geometry of simplicial…

Algebraic Topology · Mathematics 2023-11-17 Jian Liu , Ran Liu , Jie Wu