## 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**

### 2011/02/18

10:30-12:00 Room #122 (Graduate School of Math. Sci. Bldg.)

Dirac families and 1-cocycles (ENGLISH)

**Pedram Hekmati**(Univ. Adelaide)Dirac families and 1-cocycles (ENGLISH)

[ Abstract ]

Families of Dirac type operators, transforming covariantly under the projective action of the loop group $LG$, determine a class in twisted K-theory on compact Lie groups $G$. The loop group is the gauge group of a principal $G$-bundle over the circle and an interesting problem is to try to generalise the circle to a higher dimensional compact manifold. This is far from obvious and some of the difficulties can be modelled in a slightly simpler setting, by replacing $LG$ and gauge connections by objects which have only small differentiability in the Sobolev sense. In this talk, I will provide some background to this problem and explain how 1-cocycles naturally appear in this construction.

Families of Dirac type operators, transforming covariantly under the projective action of the loop group $LG$, determine a class in twisted K-theory on compact Lie groups $G$. The loop group is the gauge group of a principal $G$-bundle over the circle and an interesting problem is to try to generalise the circle to a higher dimensional compact manifold. This is far from obvious and some of the difficulties can be modelled in a slightly simpler setting, by replacing $LG$ and gauge connections by objects which have only small differentiability in the Sobolev sense. In this talk, I will provide some background to this problem and explain how 1-cocycles naturally appear in this construction.

### 2011/02/10

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

Symplectic and quantum categories (ENGLISH)

**Alan Weinstein**(UC Berkeley)Symplectic and quantum categories (ENGLISH)

### 2011/01/28

14:45-16:15 Room #122 (Graduate School of Math. Sci. Bldg.)

Semiprojectivity of graph algebras (ENGLISH)

**Takeshi Katsura**(Keio University)Semiprojectivity of graph algebras (ENGLISH)

### 2011/01/27

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

Entire Cyclic Cohomology of Noncommutative Riemann Surfaces (JAPANESE)

**Hiroshi Takai**(Tokyo Metropolitan University)Entire Cyclic Cohomology of Noncommutative Riemann Surfaces (JAPANESE)

### 2011/01/20

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

Property (TT)/T and homomorphism rigidity into Out$(F_n)$ (JAPANESE)

**Masato Mimura**(Univ. Tokyo)Property (TT)/T and homomorphism rigidity into Out$(F_n)$ (JAPANESE)

### 2011/01/18

16:30-18:00 Room #118 (Graduate School of Math. Sci. Bldg.)

Scattering induced current in a tight binding band (ENGLISH)

**Claude-Alain Pillet**(Univ. de Toulon et du Var)Scattering induced current in a tight binding band (ENGLISH)

### 2011/01/13

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

Global dimensions for fusion categories of type $(G,k)$ (ENGLISH)

**Robert Coquereaux**(CNRS/CPT)Global dimensions for fusion categories of type $(G,k)$ (ENGLISH)

### 2011/01/11

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

Noncommutative geometry and diffeomorphism-invariant geometries (ENGLISH)

**Raphael Ponge**(Univ. Tokyo)Noncommutative geometry and diffeomorphism-invariant geometries (ENGLISH)

### 2010/12/16

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

Evolution of Quantum Dynamical Systems (ENGLISH)

**Marco Merkli**(Memorial Univ. Newfoundland)Evolution of Quantum Dynamical Systems (ENGLISH)

### 2010/12/16

15:15-16:15 Room #122 (Graduate School of Math. Sci. Bldg.)

Fixed point theorems and derivations (ENGLISH)

**Nicolas Monod**(EPFL)Fixed point theorems and derivations (ENGLISH)

### 2010/12/09

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

Spectral flow associated to KMS states with periodic KMS group action (ENGLISH)

**Ryszard Nest**(Univ. Copenhagen)Spectral flow associated to KMS states with periodic KMS group action (ENGLISH)

### 2010/11/30

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

Noncommutative geometry and Rankin-Cohen brackets (ENGLISH)

**Yi-Jun Yao**(Fudan Univ.)Noncommutative geometry and Rankin-Cohen brackets (ENGLISH)

### 2010/11/25

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

Classification of actions of Kac algebras (JAPANESE)

**Reiji Tomatsu**(Tokyo Univ. Science)Classification of actions of Kac algebras (JAPANESE)

### 2010/11/18

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

Perturbation of dual operator algebras and similarity (ENGLISH)

**Jean Roydor**(Univ. Tokyo)Perturbation of dual operator algebras and similarity (ENGLISH)

### 2010/11/04

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

Nonequilibrium Statistical Mechanics (JAPANESE)

**Yoshiko Ogata**(Univ.Tokyo)Nonequilibrium Statistical Mechanics (JAPANESE)

### 2010/10/28

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

Type III representations of the infinite symmetric group (ENGLISH)

**Makoto Yamashita**(Univ. Tokyo)Type III representations of the infinite symmetric group (ENGLISH)

[ Abstract ]

Based on earlier results about the structure of the II$_1$ representations of the infinite symmetric group, we investigate its type III representations and the related inclusion of von Neumann algebras of type III.

Based on earlier results about the structure of the II$_1$ representations of the infinite symmetric group, we investigate its type III representations and the related inclusion of von Neumann algebras of type III.

### 2010/10/21

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

Free probability and entropy additivity problems for Quantum information theory (ENGLISH)

**Benoit Collins**(Univ. Ottawa)Free probability and entropy additivity problems for Quantum information theory (ENGLISH)

### 2010/10/14

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

Nonstandard analysis for operator algebraists (JAPANESE)

**Yasuyuki Kawahigashi**(Univ. Tokyo)Nonstandard analysis for operator algebraists (JAPANESE)

### 2010/07/22

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

$W^*$ Rigidity for actions of wreath product groups (ENGLISH)

**Owen Sizemore**(UCLA)$W^*$ Rigidity for actions of wreath product groups (ENGLISH)

[ Abstract ]

The past 8 years have seen much progress in the classification of

actions of groups on measure spaces. Much of this is due to new powerful

techniques in operator algebras. We will survey some of these results

as well as the new operator algebra techniques. We will then give new

results concerning the classification of actions of wreath product groups.

The past 8 years have seen much progress in the classification of

actions of groups on measure spaces. Much of this is due to new powerful

techniques in operator algebras. We will survey some of these results

as well as the new operator algebra techniques. We will then give new

results concerning the classification of actions of wreath product groups.

### 2010/07/15

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

Type II$_1$ von Neumann representations for Hecke operators on Maass forms (after F. Radulescu) (ENGLISH)

**Narutaka Ozawa**(Univ. Tokyo)Type II$_1$ von Neumann representations for Hecke operators on Maass forms (after F. Radulescu) (ENGLISH)

### 2010/07/08

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

Killing weeds with annular multiplicities $*10$ via quadratic tangles (ENGLISH)

**Dave Penneys**(UC Berkeley)Killing weeds with annular multiplicities $*10$ via quadratic tangles (ENGLISH)

[ Abstract ]

In recent work with Morrison, Peters, and Snyder, we eliminate two

families of possible principal graphs with graph norms less than 5 using

techniques derived from Jones' work on quadratic tangles.

In recent work with Morrison, Peters, and Snyder, we eliminate two

families of possible principal graphs with graph norms less than 5 using

techniques derived from Jones' work on quadratic tangles.

### 2010/07/06

16:30-18:00 Room #118 (Graduate School of Math. Sci. Bldg.)

On the Existence of the Dynamics for Anharmonic Quantum Oscillator Systems (ENGLISH)

**Robert Sims**(Univ. Arizona)On the Existence of the Dynamics for Anharmonic Quantum Oscillator Systems (ENGLISH)

### 2010/06/24

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

Strong solidity of factors from lattices in SO(n,1) and SU(n,1) (ENGLISH)

**Thomas Sinclair**(Vanderbilt Univ.)Strong solidity of factors from lattices in SO(n,1) and SU(n,1) (ENGLISH)

[ Abstract ]

Generalizing techniques found in Ozawa and Popa,

``On a class of II$_1$ factors with at most one Cartan subalgebra, II''

(Amer. J. Math., to appear), we show that the group factors of ICC

lattices in SO(n,1) and SU(n,1), $n\\ge2$, are strongly solid. If

time permits, we will also discuss applications to $L^2$-rigidity.

Generalizing techniques found in Ozawa and Popa,

``On a class of II$_1$ factors with at most one Cartan subalgebra, II''

(Amer. J. Math., to appear), we show that the group factors of ICC

lattices in SO(n,1) and SU(n,1), $n\\ge2$, are strongly solid. If

time permits, we will also discuss applications to $L^2$-rigidity.

### 2010/06/17

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

On a relative version of Wall's conjecture (ENGLISH)

**Feng Xu**(UC Riverside)On a relative version of Wall's conjecture (ENGLISH)

### 2010/06/10

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

Random groups and nonarchimedean lattices (JAPANESE)

**Mikael Pichot**(IPMU)Random groups and nonarchimedean lattices (JAPANESE)