## Operator Algebra Seminars

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

Seminar information archive

### 2010/06/03

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

### 2010/05/27

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

### 2010/04/22

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

### 2010/02/18

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

### 2010/01/19

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

Entire Cyclic Cohomology of Noncommutative Spheres

### 2010/01/14

16:30-18:00   Room #128 (Graduate School of Math. Sci. Bldg.)
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.)
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 $\\mathbb R$
David Kerr (Texas A&M Univ.) 16:30-18:00
Topological 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

### 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

### 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

### 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

### 2009/10/29

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

### 2009/09/07

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

### 2009/07/09

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

### 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

### 2009/06/18

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

The super Virasoro algebra and noncommutative geometry

### 2009/06/11

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