Hyperbolic Groupoids and Duality
Hyperbolic Groupoids and Duality

Author: Volodymyr Nekrashevych

Publisher: American Mathematical Soc.

Published: 2015-08-21

Total Pages: 120

ISBN-13: 1470415445

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The author introduces a notion of hyperbolic groupoids, generalizing the notion of a Gromov hyperbolic group. Examples of hyperbolic groupoids include actions of Gromov hyperbolic groups on their boundaries, pseudogroups generated by expanding self-coverings, natural pseudogroups acting on leaves of stable (or unstable) foliation of an Anosov diffeomorphism, etc. The author describes a duality theory for hyperbolic groupoids. He shows that for every hyperbolic groupoid G there is a naturally defined dual groupoid G⊤ acting on the Gromov boundary of a Cayley graph of G. The groupoid G⊤ is also hyperbolic and such that (G⊤)⊤ is equivalent to G. Several classes of examples of hyperbolic groupoids and their applications are discussed.

Hyperbolic Groupoids and Duality
Hyperbolic Groupoids and Duality

Author: Volodymyr Nekrashevych

Publisher:

Published: 2015

Total Pages: 108

ISBN-13: 9781470425111

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We introduce a notion of hyperbolic groupoids, generalizing the notion of a Gromov hyperbolic group. Examples of hyperbolic groupoids include actions of Gromov hyperbolic groups on their boundaries, pseudogroups generated by expanding self-coverings, natural pseudogroups acting on leaves of stable (or unstable) foliation of an Anosov diffeomorphism, etc. We describe a duality theory for hyperbolic groupoids. We show that for every hyperbolic groupoid G there is a naturally defined dual groupoid G⊤ acting on the Gromov boundary of a Cayley graph of G. The groupoid G⊤ is also hyperbolic and such that (G⊤)⊤ is equivalent to G. Several classes of examples of hyperbolic groupoids and their applications are discussed.

Geometric and Cohomological Group Theory
Geometric and Cohomological Group Theory

Author: Peter H. Kropholler

Publisher: Cambridge University Press

Published: 2017-10-19

Total Pages: 278

ISBN-13: 1108548873

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This volume provides state-of-the-art accounts of exciting recent developments in the rapidly-expanding fields of geometric and cohomological group theory. The research articles and surveys collected here demonstrate connections to such diverse areas as geometric and low-dimensional topology, analysis, homological algebra and logic. Topics include various constructions of Thompson-like groups, Wise's theory of special cube complexes, groups with exotic homological properties, the Farrell–Jones assembly conjectures and new applications of Garside structures. Its mixture of surveys and research makes this book an excellent entry point for young researchers as well as a useful reference work for experts in the field. This is the proceedings of the 100th meeting of the London Mathematical Society series of Durham Symposia.

Groups and Topological Dynamics
Groups and Topological Dynamics

Author: Volodymyr Nekrashevych

Publisher: American Mathematical Society

Published: 2022-10-11

Total Pages: 708

ISBN-13: 1470471205

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This book is devoted to group-theoretic aspects of topological dynamics such as studying groups using their actions on topological spaces, using group theory to study symbolic dynamics, and other connections between group theory and dynamical systems. One of the main applications of this approach to group theory is the study of asymptotic properties of groups such as growth and amenability. The book presents recently developed techniques of studying groups of dynamical origin using the structure of their orbits and associated groupoids of germs, applications of the iterated monodromy groups to hyperbolic dynamical systems, topological full groups and their properties, amenable groups, groups of intermediate growth, and other topics. The book is suitable for graduate students and researchers interested in group theory, transformations defined by automata, topological and holomorphic dynamics, and theory of topological groupoids. Each chapter is supplemented by exercises of various levels of complexity.

Descent Construction for GSpin Groups
Descent Construction for GSpin Groups

Author: Joseph Hundley

Publisher: American Mathematical Soc.

Published: 2016-09-06

Total Pages: 138

ISBN-13: 1470416670

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In this paper the authors provide an extension of the theory of descent of Ginzburg-Rallis-Soudry to the context of essentially self-dual representations, that is, representations which are isomorphic to the twist of their own contragredient by some Hecke character. The authors' theory supplements the recent work of Asgari-Shahidi on the functorial lift from (split and quasisplit forms of) GSpin2n to GL2n.

Irreducible Geometric Subgroups of Classical Algebraic Groups
Irreducible Geometric Subgroups of Classical Algebraic Groups

Author: Timothy C. Burness,

Publisher: American Mathematical Soc.

Published: 2016-01-25

Total Pages: 100

ISBN-13: 1470414945

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Let be a simple classical algebraic group over an algebraically closed field of characteristic with natural module . Let be a closed subgroup of and let be a non-trivial irreducible tensor-indecomposable -restricted rational -module such that the restriction of to is irreducible. In this paper the authors classify the triples of this form, where is a disconnected maximal positive-dimensional closed subgroup of preserving a natural geometric structure on .

Reduced Fusion Systems over 2-Groups of Sectional Rank at Most 4
Reduced Fusion Systems over 2-Groups of Sectional Rank at Most 4

Author: Bob Oliver

Publisher: American Mathematical Soc.

Published: 2016-01-25

Total Pages: 112

ISBN-13: 1470415488

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The author classifies all reduced, indecomposable fusion systems over finite -groups of sectional rank at most . The resulting list is very similar to that by Gorenstein and Harada of all simple groups of sectional -rank at most . But this method of proof is very different from theirs, and is based on an analysis of the essential subgroups which can occur in the fusion systems.

Symmetry Breaking for Representations of Rank One Orthogonal Groups
Symmetry Breaking for Representations of Rank One Orthogonal Groups

Author: Toshiyuki Kobayashi

Publisher: American Mathematical Soc.

Published: 2015-10-27

Total Pages: 124

ISBN-13: 147041922X

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The authors give a complete classification of intertwining operators (symmetry breaking operators) between spherical principal series representations of and . They construct three meromorphic families of the symmetry breaking operators, and find their distribution kernels and their residues at all poles explicitly. Symmetry breaking operators at exceptional discrete parameters are thoroughly studied. The authors obtain closed formulae for the functional equations which the composition of the symmetry breaking operators with the Knapp-Stein intertwining operators of and satisfy, and use them to determine the symmetry breaking operators between irreducible composition factors of the spherical principal series representations of and . Some applications are included.

Monoidal Categories and the Gerstenhaber Bracket in Hochschild Cohomology
Monoidal Categories and the Gerstenhaber Bracket in Hochschild Cohomology

Author: Reiner Hermann:

Publisher: American Mathematical Soc.

Published: 2016-09-06

Total Pages: 158

ISBN-13: 1470419955

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In this monograph, the author extends S. Schwede's exact sequence interpretation of the Gerstenhaber bracket in Hochschild cohomology to certain exact and monoidal categories. Therefore the author establishes an explicit description of an isomorphism by A. Neeman and V. Retakh, which links Ext-groups with fundamental groups of categories of extensions and relies on expressing the fundamental group of a (small) category by means of the associated Quillen groupoid. As a main result, the author shows that his construction behaves well with respect to structure preserving functors between exact monoidal categories. The author uses his main result to conclude, that the graded Lie bracket in Hochschild cohomology is an invariant under Morita equivalence. For quasi-triangular bialgebras, he further determines a significant part of the Lie bracket's kernel, and thereby proves a conjecture by L. Menichi. Along the way, the author introduces n-extension closed and entirely extension closed subcategories of abelian categories, and studies some of their properties.

Layer Potentials and Boundary-Value Problems for Second Order Elliptic Operators with Data in Besov Spaces
Layer Potentials and Boundary-Value Problems for Second Order Elliptic Operators with Data in Besov Spaces

Author: Ariel Barton:

Publisher: American Mathematical Soc.

Published: 2016-09-06

Total Pages: 122

ISBN-13: 1470419890

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This monograph presents a comprehensive treatment of second order divergence form elliptic operators with bounded measurable t-independent coefficients in spaces of fractional smoothness, in Besov and weighted Lp classes. The authors establish: (1) Mapping properties for the double and single layer potentials, as well as the Newton potential; (2) Extrapolation-type solvability results: the fact that solvability of the Dirichlet or Neumann boundary value problem at any given Lp space automatically assures their solvability in an extended range of Besov spaces; (3) Well-posedness for the non-homogeneous boundary value problems. In particular, the authors prove well-posedness of the non-homogeneous Dirichlet problem with data in Besov spaces for operators with real, not necessarily symmetric, coefficients.