Kazhdan's Property (T)

Kazhdan's Property (T)

Author: Bekka M Bachir La Harpe Pierre de Valette Alain

Publisher:

Published: 2014-05-14

Total Pages: 488

ISBN-13: 9780511395116

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A comprehensive introduction to the role of Property (T), with applications to an amazing number of fields within mathematics.


Kazhdan's Property (T)

Kazhdan's Property (T)

Author: Bachir Bekka

Publisher: Cambridge University Press

Published: 2008-04-17

Total Pages:

ISBN-13: 1139471082

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Property (T) is a rigidity property for topological groups, first formulated by D. Kazhdan in the mid 1960's with the aim of demonstrating that a large class of lattices are finitely generated. Later developments have shown that Property (T) plays an important role in an amazingly large variety of subjects, including discrete subgroups of Lie groups, ergodic theory, random walks, operator algebras, combinatorics, and theoretical computer science. This monograph offers a comprehensive introduction to the theory. It describes the two most important points of view on Property (T): the first uses a unitary group representation approach, and the second a fixed point property for affine isometric actions. Via these the authors discuss a range of important examples and applications to several domains of mathematics. A detailed appendix provides a systematic exposition of parts of the theory of group representations that are used to formulate and develop Property (T).


Introduction to Arithmetic Groups

Introduction to Arithmetic Groups

Author: Armand Borel

Publisher: American Mathematical Soc.

Published: 2019-11-07

Total Pages: 118

ISBN-13: 1470452316

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Fifty years after it made the transition from mimeographed lecture notes to a published book, Armand Borel's Introduction aux groupes arithmétiques continues to be very important for the theory of arithmetic groups. In particular, Chapter III of the book remains the standard reference for fundamental results on reduction theory, which is crucial in the study of discrete subgroups of Lie groups and the corresponding homogeneous spaces. The review of the original French version in Mathematical Reviews observes that “the style is concise and the proofs (in later sections) are often demanding of the reader.” To make the translation more approachable, numerous footnotes provide helpful comments.


Discrete Groups, Expanding Graphs and Invariant Measures

Discrete Groups, Expanding Graphs and Invariant Measures

Author: Alex Lubotzky

Publisher: Springer Science & Business Media

Published: 2010-02-17

Total Pages: 201

ISBN-13: 3034603320

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In the last ?fteen years two seemingly unrelated problems, one in computer science and the other in measure theory, were solved by amazingly similar techniques from representation theory and from analytic number theory. One problem is the - plicit construction of expanding graphs («expanders»). These are highly connected sparse graphs whose existence can be easily demonstrated but whose explicit c- struction turns out to be a dif?cult task. Since expanders serve as basic building blocks for various distributed networks, an explicit construction is highly des- able. The other problem is one posed by Ruziewicz about seventy years ago and studied by Banach [Ba]. It asks whether the Lebesgue measure is the only ?nitely additive measure of total measure one, de?ned on the Lebesgue subsets of the n-dimensional sphere and invariant under all rotations. The two problems seem, at ?rst glance, totally unrelated. It is therefore so- what surprising that both problems were solved using similar methods: initially, Kazhdan’s property (T) from representation theory of semi-simple Lie groups was applied in both cases to achieve partial results, and later on, both problems were solved using the (proved) Ramanujan conjecture from the theory of automorphic forms. The fact that representation theory and automorphic forms have anything to do with these problems is a surprise and a hint as well that the two questions are strongly related.


Groups with the Haagerup Property

Groups with the Haagerup Property

Author: Pierre-Alain Cherix

Publisher: Birkhäuser

Published: 2012-12-06

Total Pages: 130

ISBN-13: 3034882378

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A locally compact group has the Haagerup property, or is a-T-menable in the sense of Gromov, if it admits a proper isometric action on some affine Hilbert space. As Gromov's pun is trying to indicate, this definition is designed as a strong negation to Kazhdan's property (T), characterized by the fact that every isometric action on some affine Hilbert space has a fixed point. This book is to covers various aspects of the Haagerup property. It gives several new examples.


Expansion in Finite Simple Groups of Lie Type

Expansion in Finite Simple Groups of Lie Type

Author: Terence Tao

Publisher: American Mathematical Soc.

Published: 2015-04-16

Total Pages: 319

ISBN-13: 1470421968

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Expander graphs are an important tool in theoretical computer science, geometric group theory, probability, and number theory. Furthermore, the techniques used to rigorously establish the expansion property of a graph draw from such diverse areas of mathematics as representation theory, algebraic geometry, and arithmetic combinatorics. This text focuses on the latter topic in the important case of Cayley graphs on finite groups of Lie type, developing tools such as Kazhdan's property (T), quasirandomness, product estimates, escape from subvarieties, and the Balog-Szemerédi-Gowers lemma. Applications to the affine sieve of Bourgain, Gamburd, and Sarnak are also given. The material is largely self-contained, with additional sections on the general theory of expanders, spectral theory, Lie theory, and the Lang-Weil bound, as well as numerous exercises and other optional material.


Property ($T$) for Groups Graded by Root Systems

Property ($T$) for Groups Graded by Root Systems

Author: Mikhail Ershov

Publisher: American Mathematical Soc.

Published: 2017-09-25

Total Pages: 148

ISBN-13: 1470426048

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The authors introduce and study the class of groups graded by root systems. They prove that if is an irreducible classical root system of rank and is a group graded by , then under certain natural conditions on the grading, the union of the root subgroups is a Kazhdan subset of . As the main application of this theorem the authors prove that for any reduced irreducible classical root system of rank and a finitely generated commutative ring with , the Steinberg group and the elementary Chevalley group have property . They also show that there exists a group with property which maps onto all finite simple groups of Lie type and rank , thereby providing a “unified” proof of expansion in these groups.


Groups of Circle Diffeomorphisms

Groups of Circle Diffeomorphisms

Author: Andrés Navas

Publisher: University of Chicago Press

Published: 2011-06-01

Total Pages: 310

ISBN-13: 0226569500

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In recent years scholars from a variety of branches of mathematics have made several significant developments in the theory of group actions. Groups of Circle Diffeomorphisms systematically explores group actions on the simplest closed manifold, the circle. As the group of circle diffeomorphisms is an important subject in modern mathematics, this book will be of interest to those doing research in group theory, dynamical systems, low dimensional geometry and topology, and foliation theory. The book is mostly self-contained and also includes numerous complementary exercises, making it an excellent textbook for undergraduate and graduate students.