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A note on the Size-Ramsey number of long subdivisions of graphs

Jair Donadelli, Penny E. Haxell, Yoshiharu Kohayakawa (2005)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

Let T s H be the graph obtained from a given graph H by subdividing each edge s times. Motivated by a problem raised by Igor Pak [Mixing time and long paths in graphs, in Proc. of the 13th annual ACM-SIAM Symposium on Discrete Algorithms (SODA 2002) 321–328], we prove that, for any graph H , there exist graphs G with O ( s ) edges that are Ramsey with respect to T s H .

A note on the Size-Ramsey number of long subdivisions of graphs

Jair Donadelli, Penny E. Haxell, Yoshiharu Kohayakawa (2010)

RAIRO - Theoretical Informatics and Applications

Let TsH be the graph obtained from a given graph H by subdividing each edge s times. Motivated by a problem raised by Igor Pak [Mixing time and long paths in graphs, in Proc. of the 13th annual ACM-SIAM Symposium on Discrete Algorithms (SODA 2002) 321–328], we prove that, for any graph H, there exist graphs G with O(s) edges that are Ramsey with respect to TsH.

A problem of Rankin on sets without geometric progressions

Melvyn B. Nathanson, Kevin O'Bryant (2015)

Acta Arithmetica

A geometric progression of length k and integer ratio is a set of numbers of the form a , a r , . . . , a r k - 1 for some positive real number a and integer r ≥ 2. For each integer k ≥ 3, a greedy algorithm is used to construct a strictly decreasing sequence ( a i ) i = 1 of positive real numbers with a₁ = 1 such that the set G ( k ) = i = 1 ( a 2 i , a 2 i - 1 ] contains no geometric progression of length k and integer ratio. Moreover, G ( k ) is a maximal subset of (0,1] that contains no geometric progression of length k and integer ratio. It is also proved that there is...

A Ramsey-style extension of a theorem of Erdős and Hajnal

Peter Komjáth (2001)

Fundamenta Mathematicae

If n, t are natural numbers, μ is an infinite cardinal, G is an n-chromatic graph of cardinality at most μ, then there is a graph X with X ( G ) ¹ μ , |X| = μ⁺, such that every subgraph of X of cardinality < t is n-colorable.

A strongly non-Ramsey uncountable graph

Péter Komjáth (1997)

Fundamenta Mathematicae

It is consistent that there exists a graph X of cardinality 1 such that every graph has an edge coloring with 1 colors in which the induced copies of X (if there are any) are totally multicolored (get all possible colors).

About a generalization of transversals

Martin Kochol (1994)

Mathematica Bohemica

The aim of this paper is to generalize several basic results from transversal theory, primarily the theorem of Edmonds and Fulkerson.

Amenability and Ramsey theory

Justin Tatch Moore (2013)

Fundamenta Mathematicae

The purpose of this article is to connect the notion of the amenability of a discrete group with a new form of structural Ramsey theory. The Ramsey-theoretic reformulation of amenability constitutes a considerable weakening of the Følner criterion. As a by-product, it will be shown that in any non-amenable group G, there is a subset E of G such that no finitely additive probability measure on G measures all translates of E equally. The analysis of discrete groups will be generalized to the setting...

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