scholarly journals MONOID ACTIONS AND ULTRAFILTER METHODS IN RAMSEY THEORY

2019 ◽  
Vol 7 ◽  
Author(s):  
SŁAWOMIR SOLECKI
Keyword(s):  
Ramsey Theory ◽  
Algebraic Structures ◽  
Ramsey Theorem

First, we prove a theorem on dynamics of actions of monoids by endomorphisms of semigroups. Second, we introduce algebraic structures suitable for formalizing infinitary Ramsey statements and prove a theorem that such statements are implied by the existence of appropriate homomorphisms between the algebraic structures. We make a connection between the two themes above, which allows us to prove some general Ramsey theorems for sequences. We give a new proof of the Furstenberg–Katznelson Ramsey theorem; in fact, we obtain a version of this theorem that is stronger than the original one. We answer in the negative a question of Lupini on possible extensions of Gowers’ Ramsey theorem.

scholarly journals Comparisons of Polychromatic and Monochromatic Ramsey Theory

2013 ◽  
Vol 78 (3) ◽  
pp. 951-968 ◽  
Author(s):  
Justin Palumbo
Keyword(s):  
Classical Result ◽  
Ramsey Theory ◽  
Axiom Of Choice ◽  
Ramsey Theorem ◽  
Partition Relations ◽  
Combinatorial Principles ◽  
The Axiom Of Choice ◽  
Relationship Of ◽  
The Relationship ◽  
Special Classes

AbstractWe compare the strength of polychromatic and monochromatic Ramsey theory in several set-theoretic domains. We show that the rainbow Ramsey theorem does not follow from ZF, nor does the rainbow Ramsey theorem imply Ramsey's theorem over ZF. Extending the classical result of Erdős and Rado we show that the axiom of choice precludes the natural infinite exponent partition relations for polychromatic Ramsey theory. We introduce rainbow Ramsey ultrafilters, a polychromatic analogue of the usual Ramsey ultrafilters. We investigate the relationship of rainbow Ramsey ultrafilters with various special classes of ultrafilters, showing for example that every rainbow Ramsey ultrafilter is nowhere dense but rainbow Ramsey ultrafilters need not be rapid. This entails comparison of the polychromatic and monochromatic Ramsey theorems as combinatorial principles on ω.

A Ramsey Theorem with an Application to Sequences in Banach Spaces

2012 ◽  
Vol 55 (2) ◽  
pp. 410-417
Author(s):  
Robert Service
Keyword(s):  
Banach Space ◽  
Banach Spaces ◽  
Ramsey Theory ◽  
Basic Sequence ◽  
Alternative Proof ◽  
Ramsey Theorem ◽  
Combinatorial Lemma

AbstractThe notion of a maximally conditional sequence is introduced for sequences in a Banach space. It is then proved using Ramsey theory that every basic sequence in a Banach space has a subsequence which is either an unconditional basic sequence or a maximally conditional sequence. An apparently novel, purely combinatorial lemma in the spirit of Galvin's theorem is used in the proof. An alternative proof of the dichotomy result for sequences in Banach spaces is also sketched, using the Galvin–Prikry theorem.

scholarly journals A RAMSEY THEOREM ON SEMIGROUPS AND A GENERAL VAN DER CORPUT LEMMA

2016 ◽  
Vol 81 (2) ◽  
pp. 718-741 ◽  
Author(s):  
ANUSH TSERUNYAN
Keyword(s):  
Ramsey Theory ◽  
Major Theme ◽  
Multiple Recurrence ◽  
Ramsey Theorem ◽  
Arithmetic Combinatorics

AbstractA major theme in arithmetic combinatorics is proving multiple recurrence results on semigroups (such as Szemerédi’s theorem) and this can often be done using methods of ergodic Ramsey theory. What usually lies at the heart of such proofs is that, for actions of semigroups, a certain kind of one recurrence (mixing along a filter) amplifies itself to multiple recurrence. This amplification is proved using a so-called van der Corput difference lemma for a suitable filter on the semigroup. Particular instances of this lemma (for concrete filters) have been proven before (by Furstenberg, Bergelson–McCutcheon, and others), with a somewhat different proof in each case. We define a notion of differentiation for subsets of semigroups and isolate the class of filters that respect this notion. The filters in this class (call them ∂-filters) include all those for which the van der Corput lemma was known, and our main result is a van der Corput lemma for ∂-filters, which thus generalizes all its previous instances. This is done via proving a Ramsey theorem for graphs on the semigroup with edges between the semigroup elements labeled by their ratios.

scholarly journals A Dual Ramsey Theorem for Permutations

10.37236/6845 ◽  
2017 ◽  
Vol 24 (3) ◽  
Author(s):  
Dragan Mašulović
Keyword(s):  
Category Theory ◽  
Ramsey Theory ◽  
Ramsey Property ◽  
Ramsey Theorem

In 2012 M. Sokić proved that the that the class of all finite permutations has the Ramsey property. Using different strategies the same result was then reproved in 2013 by J. Böttcher and J. Foniok, in 2014 by M. Bodirsky and in 2015 yet another proof was provided by M. Sokić.Using the categorical reinterpretation of the Ramsey property in this paper we prove that the class of all finite permutations has the dual Ramsey property as well. It was Leeb who pointed out in 1970 that the use of category theory can be quite helpful both in the formulation and in the proofs of results pertaining to structural Ramsey theory. In this paper we argue that this is even more the case when dealing with the dual Ramsey property.

scholarly journals Recent results in partition (Ramsey) theory for finite lattices

1981 ◽  
Vol 35 (1-3) ◽  
pp. 185-198 ◽  
Author(s):  
Hans Jürgen Prömel ◽  
Bernd Voigt
Keyword(s):  
Ramsey Theory ◽  
Finite Lattices

Some Fixpoint Techniques in Algebraic Structures and Applications to Computer Science

1987 ◽  
Vol 10 (4) ◽  
pp. 387-413
Author(s):  
Irène Guessarian
Keyword(s):  
Logic Programming ◽  
Computer Science ◽  
Proof Theory ◽  
Algebraic Structures ◽  
Data Bases

This paper recalls some fixpoint theorems in ordered algebraic structures and surveys some ways in which these theorems are applied in computer science. We describe via examples three main types of applications: in semantics and proof theory, in logic programming and in deductive data bases.

Sign in / Sign up

Export Citation Format

Share Document