Quasi-actions on Trees

Quasi-actions on Trees PDF Author: Lee Mosher
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Quasi-actions on Trees

Quasi-actions on Trees PDF Author: Lee Mosher
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Quasi-Actions on Trees II: Finite Depth Bass-Serre Trees

Quasi-Actions on Trees II: Finite Depth Bass-Serre Trees PDF Author: Lee Mosher
Publisher: American Mathematical Soc.
ISBN: 0821847120
Category : Mathematics
Languages : en
Pages : 118

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This paper addresses questions of quasi-isometric rigidity and classification for fundamental groups of finite graphs of groups, under the assumption that the Bass-Serre tree of the graph of groups has finite depth. The main example of a finite depth graph of groups is one whose vertex and edge groups are coarse Poincare duality groups. The main theorem says that, under certain hypotheses, if $\mathcal{G}$ is a finite graph of coarse Poincare duality groups, then any finitely generated group quasi-isometric to the fundamental group of $\mathcal{G}$ is also the fundamental group of a finite graph of coarse Poincare duality groups, and any quasi-isometry between two such groups must coarsely preserve the vertex and edge spaces of their Bass-Serre trees of spaces. Besides some simple normalization hypotheses, the main hypothesis is the ``crossing graph condition'', which is imposed on each vertex group $\mathcal{G}_v$ which is an $n$-dimensional coarse Poincare duality group for which every incident edge group has positive codimension: the crossing graph of $\mathcal{G}_v$ is a graph $\epsilon_v$ that describes the pattern in which the codimension 1 edge groups incident to $\mathcal{G}_v$ are crossed by other edge groups incident to $\mathcal{G}_v$, and the crossing graph condition requires that $\epsilon_v$ be connected or empty.

Quasi-actions on Trees II

Quasi-actions on Trees II PDF Author: Lee Mosher
Publisher: American Mathematical Soc.
ISBN: 0821882538
Category : Mathematics
Languages : en
Pages : 118

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"November 2011, volume 214, number 1008 (fourth of 5 numbers)."

Chevalley Supergroups

Chevalley Supergroups PDF Author: Rita Fioresi
Publisher: American Mathematical Soc.
ISBN: 0821853007
Category : Mathematics
Languages : en
Pages : 77

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Book Description
In the framework of algebraic supergeometry, the authors give a construction of the scheme-theoretic supergeometric analogue of split reductive algebraic group-schemes, namely affine algebraic supergroups associated to simple Lie superalgebras of classical type. In particular, all Lie superalgebras of both basic and strange types are considered. This provides a unified approach to most of the algebraic supergroups considered so far in the literature, and an effective method to construct new ones. The authors' method follows the pattern of a suitable scheme-theoretic revisitation of Chevalley's construction of semisimple algebraic groups, adapted to the reductive case. As an intermediate step, they prove an existence theorem for Chevalley bases of simple classical Lie superalgebras and a PBW-like theorem for their associated Kostant superalgebras.

A von Neumann Algebra Approach to Quantum Metrics/Quantum Relations

A von Neumann Algebra Approach to Quantum Metrics/Quantum Relations PDF Author: Greg Kuperberg
Publisher: American Mathematical Soc.
ISBN: 0821853414
Category : Mathematics
Languages : en
Pages : 153

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In A von Neumann Algebra Approach to Quantum Metrics, Kuperberg and Weaver propose a new definition of quantum metric spaces, or W*-metric spaces, in the setting of von Neumann algebras. Their definition effectively reduces to the classical notion in the atomic abelian case, has both concrete and intrinsic characterizations, and admits a wide variety of tractable examples. A natural application and motivation of their theory is a mutual generalization of the standard models of classical and quantum error correction. In Quantum Relations Weaver defines a ``quantum relation'' on a von Neumann algebra $\mathcal{M}\subseteq\mathcal{B}(H)$ to be a weak* closed operator bimodule over its commutant $\mathcal{M}'$. Although this definition is framed in terms of a particular representation of $\mathcal{M}$, it is effectively representation independent. Quantum relations on $l^\infty(X)$ exactly correspond to subsets of $X^2$, i.e., relations on $X$. There is also a good definition of a ``measurable relation'' on a measure space, to which quantum relations partially reduce in the general abelian case. By analogy with the classical setting, Weaver can identify structures such as quantum equivalence relations, quantum partial orders, and quantum graphs, and he can generalize Arveson's fundamental work on weak* closed operator algebras containing a masa to these cases. He is also able to intrinsically characterize the quantum relations on $\mathcal{M}$ in terms of families of projections in $\mathcal{M}{\overline{\otimes}} \mathcal{B}(l^2)$.

Dimer Models and Calabi-Yau Algebras

Dimer Models and Calabi-Yau Algebras PDF Author: Nathan Broomhead
Publisher: American Mathematical Soc.
ISBN: 0821853082
Category : Mathematics
Languages : en
Pages : 101

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Book Description
In this article the author uses techniques from algebraic geometry and homological algebra, together with ideas from string theory to construct a class of 3-dimensional Calabi-Yau algebras. The Calabi-Yau property appears throughout geometry and string theory and is increasingly being studied in algebra. He further shows that the algebras constructed are examples of non-commutative crepant resolutions (NCCRs), in the sense of Van den Bergh, of Gorenstein affine toric threefolds. Dimer models, first studied in theoretical physics, give a way of writing down a class of non-commutative algebras, as the path algebra of a quiver with relations obtained from a `superpotential'. Some examples are Calabi-Yau and some are not. The author considers two types of `consistency' conditions on dimer models, and shows that a `geometrically consistent' dimer model is `algebraically consistent'. He proves that the algebras obtained from algebraically consistent dimer models are 3-dimensional Calabi-Yau algebras. This is the key step which allows him to prove that these algebras are NCCRs of the Gorenstein affine toric threefolds associated to the dimer models.

Constructing Group Actions on Quasi-trees and Applications to Mapping Class Groups

Constructing Group Actions on Quasi-trees and Applications to Mapping Class Groups PDF Author: Mladen Bestvina
Publisher:
ISBN:
Category :
Languages : en
Pages : 335

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Non-commutative Cryptography and Complexity of Group-theoretic Problems

Non-commutative Cryptography and Complexity of Group-theoretic Problems PDF Author: Alexei G. Myasnikov
Publisher: American Mathematical Soc.
ISBN: 0821853600
Category : Computers
Languages : en
Pages : 402

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Book Description
Examines the relationship between three different areas of mathematics and theoretical computer science: combinatorial group theory, cryptography, and complexity theory. It explores how non-commutative (infinite) groups can be used in public key cryptography. It also shows that there is remarkable feedback from cryptography to combinatorial group theory because some of the problems motivated by cryptography appear to be new to group theory.

New Directions in Locally Compact Groups

New Directions in Locally Compact Groups PDF Author: Pierre-Emmanuel Caprace
Publisher: Cambridge University Press
ISBN: 1108349544
Category : Mathematics
Languages : en
Pages : 367

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Book Description
This collection of expository articles by a range of established experts and newer researchers provides an overview of the recent developments in the theory of locally compact groups. It includes introductory articles on totally disconnected locally compact groups, profinite groups, p-adic Lie groups and the metric geometry of locally compact groups. Concrete examples, including groups acting on trees and Neretin groups, are discussed in detail. An outline of the emerging structure theory of locally compact groups beyond the connected case is presented through three complementary approaches: Willis' theory of the scale function, global decompositions by means of subnormal series, and the local approach relying on the structure lattice. An introduction to lattices, invariant random subgroups and L2-invariants, and a brief account of the Burger–Mozes construction of simple lattices are also included. A final chapter collects various problems suggesting future research directions.

Mathematical Reviews

Mathematical Reviews PDF Author:
Publisher:
ISBN:
Category : Mathematics
Languages : en
Pages : 884

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