Borel Equivalence Relations

Borel Equivalence Relations PDF Author: Vladimir Grigorʹevich Kanoveĭ
Publisher: American Mathematical Soc.
ISBN: 0821844539
Category : Mathematics
Languages : en
Pages : 254

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Book Description
"Over the last 20 years, the theory of Borel equivalence relations and related topics have been very active areas of research in set theory and have important interactions with other fields of mathematics, like ergodic theory and topological dynamics, group theory, combinatorics, functional analysis, and model theory. The book presents, for the first time in mathematical literature, all major aspects of this theory and its applications."--BOOK JACKET.

Borel Equivalence Relations

Borel Equivalence Relations PDF Author: Vladimir Grigorʹevich Kanoveĭ
Publisher: American Mathematical Soc.
ISBN: 0821844539
Category : Mathematics
Languages : en
Pages : 254

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Book Description
"Over the last 20 years, the theory of Borel equivalence relations and related topics have been very active areas of research in set theory and have important interactions with other fields of mathematics, like ergodic theory and topological dynamics, group theory, combinatorics, functional analysis, and model theory. The book presents, for the first time in mathematical literature, all major aspects of this theory and its applications."--BOOK JACKET.

Rigidity Theorems for Actions of Product Groups and Countable Borel Equivalence Relations

Rigidity Theorems for Actions of Product Groups and Countable Borel Equivalence Relations PDF Author: Greg Hjorth
Publisher: American Mathematical Soc.
ISBN: 0821837710
Category : Mathematics
Languages : en
Pages : 109

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Book Description
This memoir is both a contribution to the theory of Borel equivalence relations, considered up to Borel reducibility, and measure preserving group actions considered up to orbit equivalence. Here $E$ is said to be Borel reducible to $F$ if there is a Borel function $f$ with $x E y$ if and only if $f(x) F f(y)$. Moreover, $E$ is orbit equivalent to $F$ if the respective measure spaces equipped with the extra structure provided by the equivalence relations are almost everywhere isomorphic. We consider product groups acting ergodically and by measure preserving transformations on standard Borel probability spaces.In general terms, the basic parts of the monograph show that if the groups involved have a suitable notion of 'boundary' (we make this precise with the definition of near hyperbolic), then one orbit equivalence relation can only be Borel reduced to another if there is some kind of algebraic resemblance between the product groups and coupling of the action. This also has consequence for orbit equivalence. In the case that the original equivalence relations do not have non-trivial almost invariant sets, the techniques lead to relative ergodicity results. An equivalence relation $E$ is said to be relatively ergodic to $F$ if any $f$ with $xEy \Rightarrow f(x) F f(y)$ has $[f(x)]_F$ constant almost everywhere.This underlying collection of lemmas and structural theorems is employed in a number of different ways. In the later parts of the paper, we give applications of the theory to specific cases of product groups. In particular, we catalog the actions of products of the free group and obtain additional rigidity theorems and relative ergodicity results in this context. There is a rather long series of appendices, whose primary goal is to give the reader a comprehensive account of the basic techniques. But included here are also some new results. For instance, we show that the Furstenberg-Zimmer lemma on cocycles from amenable groups fails with respect to Baire category, and use this to answer a question of Weiss. We also present a different proof that $F_2$ has the Haagerup approximation property.

Classification and Orbit Equivalence Relations

Classification and Orbit Equivalence Relations PDF Author: Greg Hjorth
Publisher: American Mathematical Soc.
ISBN: 0821820028
Category : Mathematics
Languages : en
Pages : 217

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Book Description
Actions of Polish groups are ubiquitous in mathematics. In certain branches of ergodic theory and functional analysis, one finds a systematic study of the group of measure-preserving transformations and the unitary group. In logic, the analysis of countable models intertwines with results concerning the actions of the infinite symmetric group. This text develops the theory of Polish group actions entirely from scratch, ultimately presenting a coherent theory of the resulting orbit equivalence classes that may allow complete classification by invariants of an indicated form. The book concludes with a criterion for an orbit equivalence relation classifiable by countable structures considered up to isomorphism. This self-contained volume offers a complete treatment of this active area of current research and develops a difficult general theory classifying a class of mathematical objects up to some relevant notion of isomorphism or equivalence.

Descriptive Set Theory and Dynamical Systems

Descriptive Set Theory and Dynamical Systems PDF Author: M. Foreman
Publisher: Cambridge University Press
ISBN: 9780521786447
Category : Mathematics
Languages : en
Pages : 304

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Book Description
This volume, first published in 2000, contains a collection of survey papers providing an introduction for graduate students and researchers in these fields.

Algebraic Ideas in Ergodic Theory

Algebraic Ideas in Ergodic Theory PDF Author: Klaus Schmidt
Publisher: American Mathematical Soc.
ISBN: 9780821889206
Category : Mathematics
Languages : en
Pages : 104

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Book Description


Topics in Orbit Equivalence

Topics in Orbit Equivalence PDF Author: Alexander Kechris
Publisher: Springer
ISBN: 3540445080
Category : Mathematics
Languages : en
Pages : 144

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Book Description
This volume provides a self-contained introduction to some topics in orbit equivalence theory, a branch of ergodic theory. The first two chapters focus on hyperfiniteness and amenability. Included here are proofs of Dye's theorem that probability measure-preserving, ergodic actions of the integers are orbit equivalent and of the theorem of Connes-Feldman-Weiss identifying amenability and hyperfiniteness for non-singular equivalence relations. The presentation here is often influenced by descriptive set theory, and Borel and generic analogs of various results are discussed. The final chapter is a detailed account of Gaboriau's recent results on the theory of costs for equivalence relations and groups and its applications to proving rigidity theorems for actions of free groups.

Topics in Orbit Equivalence

Topics in Orbit Equivalence PDF Author: Alexander S. Kechris
Publisher: Springer Science & Business Media
ISBN: 9783540226031
Category : Computers
Languages : en
Pages : 148

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Book Description
This volume provides a self-contained introduction to some topics in orbit equivalence theory, a branch of ergodic theory. The first two chapters focus on hyperfiniteness and amenability. Included here are proofs of Dye's theorem that probability measure-preserving, ergodic actions of the integers are orbit equivalent and of the theorem of Connes-Feldman-Weiss identifying amenability and hyperfiniteness for non-singular equivalence relations. The presentation here is often influenced by descriptive set theory, and Borel and generic analogs of various results are discussed. The final chapter is a detailed account of Gaboriau's recent results on the theory of costs for equivalence relations and groups and its applications to proving rigidity theorems for actions of free groups.

The Theory of Countable Borel Equivalence Relations

The Theory of Countable Borel Equivalence Relations PDF Author: Alexander S. Kechris
Publisher: Cambridge University Press
ISBN: 9781009562294
Category : Mathematics
Languages : en
Pages : 0

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Book Description
The theory of definable equivalence relations has been a vibrant area of research in descriptive set theory for the past three decades. It serves as a foundation of a theory of complexity of classification problems in mathematics and is further motivated by the study of group actions in a descriptive, topological, or measure-theoretic context. A key part of this theory is concerned with the structure of countable Borel equivalence relations. These are exactly the equivalence relations generated by Borel actions of countable discrete groups and this introduces important connections with group theory, dynamical systems, and operator algebras. This text surveys the state of the art in the theory of countable Borel equivalence relations and delineates its future directions and challenges. It gives beginning graduate students and researchers a bird's-eye view of the subject, with detailed references to the extensive literature provided for further study.

Classical and New Paradigms of Computation and their Complexity Hierarchies

Classical and New Paradigms of Computation and their Complexity Hierarchies PDF Author: Benedikt Löwe
Publisher: Springer Science & Business Media
ISBN: 1402027761
Category : Computers
Languages : en
Pages : 266

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Book Description
The notion of complexity is an important contribution of logic to theoretical computer science and mathematics. This volume attempts to approach complexity in a holistic way, investigating mathematical properties of complexity hierarchies at the same time as discussing algorithms and computational properties. A main focus of the volume is on some of the new paradigms of computation, among them Quantum Computing and Infinitary Computation. The papers in the volume are tied together by an introductory article describing abstract properties of complexity hierarchies. This volume will be of great interest to both mathematical logicians and theoretical computer scientists, providing them with new insights into the various views of complexity and thus shedding new light on their own research.

Group Colorings and Bernoulli Subflows

Group Colorings and Bernoulli Subflows PDF Author: Su Gao
Publisher: American Mathematical Soc.
ISBN: 1470418479
Category : Bernoulli numbers
Languages : en
Pages : 241

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Book Description
In this paper the authors study the dynamics of Bernoulli flows and their subflows over general countable groups. One of the main themes of this paper is to establish the correspondence between the topological and the symbolic perspectives. From the topological perspective, the authors are particularly interested in free subflows (subflows in which every point has trivial stabilizer), minimal subflows, disjointness of subflows, and the problem of classifying subflows up to topological conjugacy. Their main tool to study free subflows will be the notion of hyper aperiodic points; a point is hyper aperiodic if the closure of its orbit is a free subflow.