# Kyoto Operator Algebra Seminar

Organizers: Benoit COLLINS, Masaki IZUMI, Narutaka OZAWA.
Time and Location: 15:00 - 16:30 on Tuesday at RIMS 206
Seminar Description: This seminar features both research and introductory talks on topics in Operator Algebra, Noncommutative Geometry, Ergodic Theory, and Group Theory of various kinds (geometric, measure theoretic, functional analytic, etc.). The talks are informal and take between an hour and an hour and a half.
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Memento: 2011  2012  2013  2014  2015  2016  2017 Summer

## 2017 Fall/Winter

 Sep. 04-06 RIMS 111 Recent developments in operator algebras (program) Oct. 05 DT seminar 15:00 - 16:30 Sci 6-609 Raphael Ponge (Seoul) Cyclic homology and group actions on manifolds Oct. 11 Colloquim 16:30 - 17:30 RIMS 110 Mikael Pichot (McGill/RIMS) Nonpositive curvature and operator algebras The field of operator algebras was begun in the late 1920's by J. von Neumann, through his work on abstract Hilbert spaces and the foundation of quantum mechanics. The subject developed steadily for nearly a century, and found deep connections with many branches of mathematics. The talk will discuss, using concrete examples, some of these connections, in particular with group theory and geometry of nonpositive curvature. The main focus will be the recent work of Sylvain Barré and myself on intermediate rank geometry. I will give some motivation for this work, and explain some of the leading ideas in the study of discrete groups of intermediate rank. Oct. 17 15:00 - 16:30 RIMS 206 Masaki Izumi (Kyoto) Group Actions on Kirchberg Algebras Oct. 31 DT Seminar 15:00 - 16:30 Sci 6-609 François Dahmani (Grenoble) Conjugacy of automorphisms: on the conjugacy problem for certain automorphisms of free groups Nov. 01 Séminaire de travail 13:30 - RIMS 109 Yuki Arano (Kyoto) Maharam Nov. 07 DT Seminar 15:00 - 16:30 Sci 6-609 Tomohiro Fukaya (TMU) Coarse Cartan-Hadamard theorem and an application to the coarse Baum-Connes conjecture Nov. 14 15:00 - 16:30 RIMS 206 Yoshikata Kida (Tokyo) Central sequences in the full group and compact extensions We discuss when an orbit equivalence relation admis a non-trivial central sequence in its full group. Among others, we show that existence of such a sequence is stable under compact extension of equivalence relations. Related results and examples are also discussed. Nov. 15 Séminaire de travail 13:30 - RIMS 109 Takuya Takeishi (RIMS) Semigroup actions and K-theory (after arxiv:1205.5412) Nov. 17-19 Ritsumei BKC Annual Meeting on operator theory & operator algebra theory Nov. 21 15:00 - 16:30 RIMS 206 Kei Hasegawa (Kyushu) Boundary rigidity for free product C*-algebras For a reduced free product of C*-algebras, we prove a boundary rigidity result for the embedding of it into the associated crossed product'' C*-algebra under the assumption that the GNS representations associated with the distinguished states are essential and one of free components satisfies a suitable diffuseness condition. This provides new examples of rigid embeddings of exact C*-algebras into purely infinite simple nuclear C*-algebras. Nov. 22 Séminaire de travail 13:30 - RIMS 109 Yusuke Isono (RIMS) Locally compact group actions and Cartan rigidity (after arxiv:1703.09092) Nov. 28 15:00 - 16:30 RIMS 206 Narutaka Ozawa (RIMS) Kazhdan's property (T) and semidefinite programming Kazhdan's property (T) for groups has a number of applications in pure and applied mathematics. It has long been thought that groups with property (T) are rare among the "naturally-occurring" groups, but it may not be so and it may be possible to observe this by extensive computer calculations. After an introduction, I will present a computer assisted (but mathematically rigorous) method of confirming property (T) based on semidefinite programming with some operator algebraic input. I will report the progress recently made in collaboration with M. Kaluba, P. Nowak, and PL-grid, a Polish supercomputer. It confirms property (T) of Aut(F_5), which solves a well-known problem in geometric group theory, at least partially, leaving the tantalizing question in the case of Aut(F_d), d=4 and d>5, unsettled. Dec. 01 DS Seminar 14:00 - 17:00 Sci 6-609 Masaki Tsukamoto (Kyoto) Expansive multiparameter actions and mean dimension Dec. 05 15:00 - 16:30 RIMS 206 Mikael Pichot (McGill/RIMS) On Aut(F_2) I will explain things related to the automorphism group of $F_2$ from a geometric perspective. Dec. 09 OKU Tennōji Kansai Seminar Dec. 11 VOA workshop 10:00 - 10:50 RIMS 420 Yasuyuki Kawahigashi (Tokyo) Representation theories of vertex operator algebras and operator algebras Dec. 19 15:00 - 16:30 RIMS 206 Makoto Yamashita (Ochanomizu) Tube representations of graded categories We study the structure of tube algebra under graded twist of tensor categories. This deformation scheme played a central role in the Kazhdan-Wenzl classification of semisimple tensor categories with the fusion rules of $\mathrm{SL}_n$, and at the simplest case it relates quantum $\mathrm{SU}(2)$ group at the parameter $q$ and $-q$. Motivated by the 2-cocycle deformation result for tube algebras of pointed categories due to Bisch, Das, Ghosh, Rakshit, we give a general formula describing annular algebra of 3-cocycle deformation categories as 2-cocycle deformation of Fell bundle over a groupoid. Based on joint work with Bhowmick, Ghosh, Rakshit. Dec. 20 Séminaire de travail 13:30 - RIMS 109 Yuki Arano (Kyoto) Subfactor Jan. 09 15:00 - 16:30 RIMS 206 Jean Roydor (Bordeaux/Jussieu) Banach-Mazur stability of von Neumann algebras We study perturbation of von Neumann algebras relatively to the Banach-Mazur distance. We prove that, under some cohomological conditions, two von Neumann algebras which are close are necessarily Jordan isomorphic (thus isometric). Jan. 23 15:00 - 16:30 RIMS 206 Ulrich Pennig (Cardiff) A Dixmier-Douady theory for strongly self-absorbing C*-algebras I will report on joint work with Marius Dadarlat. We showed that the Dixmier-Douady theory of continuous fields of C*-algebras with compact operators as fibres extends to a more general theory of fields with fibres stabilised strongly self-absorbing C*-algebras. The classification of the corresponding locally trivial fields involves a generalised cohomology theory obtained from the unit spectrum of topological K-Theory, which is computable via the Atiyah-Hirzebruch spectral sequence. An important feature is the appearance of characteristic classes in higher dimensions. We found a necessary and sufficient K-theoretical condition for local triviality of these continuous fields over spaces of finite covering dimension. Jan. 24-26 RIMS 420 Mathematical study on topological phases (program) Feb. 06 15:00 - 16:30 RIMS 206 Hao-Wei Huang (Sun Yat-sen Univ) TBA Feb. 16 Friday ** RIMS ** Sven Raum (EPFL) TBA ** RIMS ** Xin Li (QMUL) TBA

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