## Operator Algebra Seminars

Seminar information archive ～10/26｜Next seminar｜Future seminars 10/27～

Date, time & place | Wednesday 16:30 - 18:00 122Room #122 (Graduate School of Math. Sci. Bldg.) |
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**Seminar information archive**

### 2010/06/03

16:30-18:00 Room #122 (Graduate School of Math. Sci. Bldg.)

Fixed Points in the Stone-Cech boundary of Groups (ENGLISH)

**Makoto Yamashita**(Univ. Tokyo)Fixed Points in the Stone-Cech boundary of Groups (ENGLISH)

[ Abstract ]

We discuss the class of discrete groups which admit fixed points under the adjoint action on the Stone-Cech boundary. Such groups have vanishing $L^2$-Betti numbers, and nonamenable ones fail to have property (AO).

We discuss the class of discrete groups which admit fixed points under the adjoint action on the Stone-Cech boundary. Such groups have vanishing $L^2$-Betti numbers, and nonamenable ones fail to have property (AO).

### 2010/05/27

16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

The C*-algebra of codimension one foliations which are almost without holonomy (ENGLISH)

**Catherine Oikonomides**(Univ. Tokyo)The C*-algebra of codimension one foliations which are almost without holonomy (ENGLISH)

### 2010/05/06

16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Connes-Landi Deformation of Spectral Triples (ENGLISH)

**Makoto Yamashita**(Univ. Tokyo)Connes-Landi Deformation of Spectral Triples (ENGLISH)

[ Abstract ]

We describe a way to deform spectral triples with a 2-torus action and a real deformation parameter, motivated by deformation of manifolds after Connes-Landi. Such deformations are shown to have naturally isomorphic K-theoretic invariants independent of the deformation parameter.

We describe a way to deform spectral triples with a 2-torus action and a real deformation parameter, motivated by deformation of manifolds after Connes-Landi. Such deformations are shown to have naturally isomorphic K-theoretic invariants independent of the deformation parameter.

### 2010/04/22

16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

The Baum-Connes Conjecture and Group Representations (ENGLISH)

**Nigel Higson**(Pennsylvania State Univ.)The Baum-Connes Conjecture and Group Representations (ENGLISH)

[ Abstract ]

The Baum-Connes conjecture asserts a sort of duality between the reduced unitary dual of a group and (a variant of) the classifying space of the group. The conjectured duality occurs at the level of K-theory. For example, for free abelian groups it amounts to a K-theoretic form of Fourier-Mukai duality. The conjecture has well-known applications in topology and geometry, but it also resonates in various ways with Lie groups and representation theory. I'll try to indicate how this comes about, and then focus on a fairly new aspect of the relationship that develops some early ideas of Mackey.

The Baum-Connes conjecture asserts a sort of duality between the reduced unitary dual of a group and (a variant of) the classifying space of the group. The conjectured duality occurs at the level of K-theory. For example, for free abelian groups it amounts to a K-theoretic form of Fourier-Mukai duality. The conjecture has well-known applications in topology and geometry, but it also resonates in various ways with Lie groups and representation theory. I'll try to indicate how this comes about, and then focus on a fairly new aspect of the relationship that develops some early ideas of Mackey.

### 2010/02/18

16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Von Neumann Algebras and Boundary Quantum Field Theory

**Roberto Longo**(University of Rome, Tor Vergata)Von Neumann Algebras and Boundary Quantum Field Theory

### 2010/01/21

16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

On Subfactors Arising from Asymptotic Representations of Symmetric Groups

**山下真**(東大数理)On Subfactors Arising from Asymptotic Representations of Symmetric Groups

### 2010/01/19

16:30-18:00 Room #126 (Graduate School of Math. Sci. Bldg.)

Entire Cyclic Cohomology of Noncommutative Spheres

**高井博司**(首都大学東京)Entire Cyclic Cohomology of Noncommutative Spheres

### 2010/01/14

16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Applications of operator algebras in Quantum information theory

**Marius Junge**(Univ. Illinois, Urbana-Champaign)Applications of operator algebras in Quantum information theory

### 2010/01/07

16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Large deviations, Billiards, and Non-equilibrium Statistical Mechanics

**Luc Rey-Bellet**(Univ. Massachusetts)Large deviations, Billiards, and Non-equilibrium Statistical Mechanics

### 2009/12/22

14:40-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Symmetric representations of the group of diffeomorphisms of $\\mathbb R$

Topological entropy for actions of sofic groups

**谷本溶**(Univ. Roma ``Tor Vergata'') 14:40-16:10Symmetric representations of the group of diffeomorphisms of $\\mathbb R$

**David Kerr**(Texas A&M Univ.) 16:30-18:00Topological entropy for actions of sofic groups

### 2009/12/17

16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Almost commuting unitaries and ${\\mathbb{Z}}^2$-action

**佐藤康彦**(北海道大理)Almost commuting unitaries and ${\\mathbb{Z}}^2$-action

### 2009/12/10

16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Symmetric norms and spaces of operators modelled on a semifinite von Neumann algebra

**張欽**(東大数理)Symmetric norms and spaces of operators modelled on a semifinite von Neumann algebra

### 2009/12/03

16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Vanishing of quasi-homomorphisms and the stable commutator

lengths on special linear groups over euclidean rings

**見村万佐人**(東大数理)Vanishing of quasi-homomorphisms and the stable commutator

lengths on special linear groups over euclidean rings

### 2009/11/12

16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Recent results for amalgamated free products of type II$_1$ factors

**酒匂宏樹**(東大数理)Recent results for amalgamated free products of type II$_1$ factors

### 2009/10/29

16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Fusion graphs for Lie groups at level k and quantum symmetries

**Robert Coquereaux**(CNRS/CPT, Marseille)Fusion graphs for Lie groups at level k and quantum symmetries

### 2009/10/22

16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

On some questions related to Voiculescu's noncommutative topological entropy

**Adam Skalski**(Lancaster University)On some questions related to Voiculescu's noncommutative topological entropy

### 2009/09/07

17:00-18:30 Room #056 (Graduate School of Math. Sci. Bldg.)

Generalized Gaussian field, theta function of Jacobi and functor of second quantization

**Marek Bozejko**(University of Wroclaw)Generalized Gaussian field, theta function of Jacobi and functor of second quantization

### 2009/07/23

16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)

Cyclic cohomology and the Novikov conjecture

**Catherine Oikonomides**(慶応大理工)Cyclic cohomology and the Novikov conjecture

### 2009/07/16

16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)

Algebraic structures in conformal field theory

**Ingo Runkel**(King's College London)Algebraic structures in conformal field theory

[ Abstract ]

It turned out to be fruitful to isolate questions in CFT which can be formulated in a purely categorical fashion. The way left and right moving degrees of freedom can be combined to a consistent theory is an example of this, the relevant structure being a commutative symmetric Frobenius algebra. This is true independently of whether CFT is formulated via sewing of surfaces or nets of operator algebras. Another example is modular invariance, which has a surprising alternative formulation as a certain maximality condition.

It turned out to be fruitful to isolate questions in CFT which can be formulated in a purely categorical fashion. The way left and right moving degrees of freedom can be combined to a consistent theory is an example of this, the relevant structure being a commutative symmetric Frobenius algebra. This is true independently of whether CFT is formulated via sewing of surfaces or nets of operator algebras. Another example is modular invariance, which has a surprising alternative formulation as a certain maximality condition.

### 2009/07/09

16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)

Examples of groups of intermediate rank

**Mikael Pichot**(東大数物連携宇宙研究機構)Examples of groups of intermediate rank

### 2009/07/02

17:00-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)

Dixmier's Similarity Problem ---Littlewood and Forests--- (一般の数学者向け)

**小沢登高**(東大数理)Dixmier's Similarity Problem ---Littlewood and Forests--- (一般の数学者向け)

### 2009/06/25

16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)

Infrared divergence of scalar quantum field model on pseudo Riemann manifold

**鈴木章斗**(九州大学数理学研究院)Infrared divergence of scalar quantum field model on pseudo Riemann manifold

### 2009/06/18

16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)

The super Virasoro algebra and noncommutative geometry

**河東泰之**(東大数理)The super Virasoro algebra and noncommutative geometry

### 2009/06/11

16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)

A topos for algebraic quantum theory

**Chris Heunen**(Radboud Universiteit Nijmegen)A topos for algebraic quantum theory

### 2009/06/04

16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)

Determinant for rectangular martices

**中神祥臣**(日本女子大)Determinant for rectangular martices