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Operator Algebra Seminars
Seminar information archive ～10/16｜Next seminar｜Future seminars 10/17～
| Date, time & place | Monday 15:30 - 17:00 Room # (Graduate School of Math. Sci. Bldg.) |
|---|---|
| Organizer(s) | MATUI Hiroki, KIDA Yoshikata, KAWAHIGASHI Yasuyuki |
Future seminars
2026/10/19
15:30-17:00 Room # 126 (Graduate School of Math. Sci. Bldg.)
Xin-Hai Tong (The University of Tokyo)
Clustering Theorem for Bose--Hubbard class Gibbs states
Xin-Hai Tong (The University of Tokyo)
Clustering Theorem for Bose--Hubbard class Gibbs states
2026/10/26
15:30-17:00 Room # 126 (Graduate School of Math. Sci. Bldg.)
Miho Mukohara (Kyushu University )
C*-discrete inclusions and approximations by finite-index bimodules
Miho Mukohara (Kyushu University )
C*-discrete inclusions and approximations by finite-index bimodules
2026/11/02
15:30-17:00 Room # 126 (Graduate School of Math. Sci. Bldg.)
Michiya Mori (Niigata University)
Isometries between C*-algebras with finite corank
Michiya Mori (Niigata University)
Isometries between C*-algebras with finite corank
[ Abstract ]
In this talk, we give a characterization of linear isometries with finite corank between two arbitrary unital C*-algebras in terms of Jordan *-homomorphisms and “finite-dimensional remainders”. Also, the corresponding results are given for linear isometries and linear order embeddings between self-adjoint parts of C*-algebras. In the finite-dimensional case, we give new examples of linear isometries between matrix algebras. This talk is based on arXiv:2607.13367.
In this talk, we give a characterization of linear isometries with finite corank between two arbitrary unital C*-algebras in terms of Jordan *-homomorphisms and “finite-dimensional remainders”. Also, the corresponding results are given for linear isometries and linear order embeddings between self-adjoint parts of C*-algebras. In the finite-dimensional case, we give new examples of linear isometries between matrix algebras. This talk is based on arXiv:2607.13367.
2026/11/09
15:30-17:00 Room # 126 (Graduate School of Math. Sci. Bldg.)
Hikaru Sekiyama (Keio University)
KS-Groupoids and KS-Crossed Products associated with Inverse Semigroup Actions
Hikaru Sekiyama (Keio University)
KS-Groupoids and KS-Crossed Products associated with Inverse Semigroup Actions
2026/11/16
15:30-17:00 Room # 126 (Graduate School of Math. Sci. Bldg.)
Kohki Sakamoto (The University of Tokyo)
TBA
Kohki Sakamoto (The University of Tokyo)
TBA
2026/11/30
15:30-17:00 Room #126 (Graduate School of Math. Sci. Bldg.)
Fuyuta Komura (Kyushu Institute of Technology)
Cartan-preserving *-automorphism groups: realization and obstructions for compact abelian groups
Fuyuta Komura (Kyushu Institute of Technology)
Cartan-preserving *-automorphism groups: realization and obstructions for compact abelian groups
[ Abstract ]
In this talk, we investigate automorphism groups preserving Cartan subalgebras of C*-algebras. First, we describe these groups in terms of automorphisms and 1-cocycles of twisted étale groupoids. As a consequence, we obtain a C*-algebraic analogue of a theorem of Feldman and Moore on Cartan-preserving automorphisms of von Neumann algebras. We then study Cartan-fixing automorphism groups. We show that every UCT Kirchberg algebra admits a Cartan subalgebra whose Cartan-fixing automorphism group contains every second countable compact abelian group. In contrast, for C*-algebras arising from expansive effective groupoids, we prove that compact Cartan-fixing automorphism groups must have finitely generated Pontryagin duals if the fixed point subalgebras are prime. As an application, we establish the existence of inequivalent Cartan subalgebras for Kirchberg algebras arising from expansive effective groupoids.
In this talk, we investigate automorphism groups preserving Cartan subalgebras of C*-algebras. First, we describe these groups in terms of automorphisms and 1-cocycles of twisted étale groupoids. As a consequence, we obtain a C*-algebraic analogue of a theorem of Feldman and Moore on Cartan-preserving automorphisms of von Neumann algebras. We then study Cartan-fixing automorphism groups. We show that every UCT Kirchberg algebra admits a Cartan subalgebra whose Cartan-fixing automorphism group contains every second countable compact abelian group. In contrast, for C*-algebras arising from expansive effective groupoids, we prove that compact Cartan-fixing automorphism groups must have finitely generated Pontryagin duals if the fixed point subalgebras are prime. As an application, we establish the existence of inequivalent Cartan subalgebras for Kirchberg algebras arising from expansive effective groupoids.
2026/12/07
15:30-17:00 Room # 126 (Graduate School of Math. Sci. Bldg.)
Akihiro Miyagawa (Kyoto University)
TBA
Akihiro Miyagawa (Kyoto University)
TBA
2026/12/14
15:30-17:00 Room # 126 (Graduate School of Math. Sci. Bldg.)
Yuki Arano (Nagoya University)
Prime actions of compact groups on von Neumann algebras
Yuki Arano (Nagoya University)
Prime actions of compact groups on von Neumann algebras
2027/01/18
15:30-17:00 Room # 126 (Graduate School of Math. Sci. Bldg.)
Katsunori Fujie (Aichi Prefectural University)
TBA
Katsunori Fujie (Aichi Prefectural University)
TBA
