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作用素環セミナー
過去の記録 ～11/02｜次回の予定｜今後の予定 11/03～
| 開催情報 | 月曜日 15:30～17:00 数理科学研究科棟(駒場) 号室 |
|---|---|
| 担当者 | 松井 宏樹、木田 良才、河東 泰之 |
| セミナーURL | https://sites.google.com/view/hirokimatui/tokyo-seminar |
今後の予定
2026年11月09日(月)
15:30-17:00 数理科学研究科棟(駒場) 126号室
關山 輝流 氏 (慶應義塾大学)
KS-Groupoids and KS-Crossed Products associated with Inverse Semigroup Actions
關山 輝流 氏 (慶應義塾大学)
KS-Groupoids and KS-Crossed Products associated with Inverse Semigroup Actions
2026年11月16日(月)
15:30-17:00 数理科学研究科棟(駒場) 126号室
阪本 皓貴 氏 (東大数理)
Continuity results for random walks in hyperbolic percolation
阪本 皓貴 氏 (東大数理)
Continuity results for random walks in hyperbolic percolation
[ 講演概要 ]
Benjamini, Lyons, and Schramm proved that the simple random walk on the infinite cluster of supercritical Bernoulli percolation exhibits positive drift and entropy, provided the underlying graph is the Cayley graph of a non-amenable group. A natural question then arises: how do these asymptotic quantities vary with the percolation parameter? In this talk, I will provide some background on this topic and show that these quantities are continuous in the parameter when the group is Gromov hyperbolic. I will also discuss how this continuity contrasts with the conjectured behavior of the Hausdorff dimension of the limit set.
Benjamini, Lyons, and Schramm proved that the simple random walk on the infinite cluster of supercritical Bernoulli percolation exhibits positive drift and entropy, provided the underlying graph is the Cayley graph of a non-amenable group. A natural question then arises: how do these asymptotic quantities vary with the percolation parameter? In this talk, I will provide some background on this topic and show that these quantities are continuous in the parameter when the group is Gromov hyperbolic. I will also discuss how this continuity contrasts with the conjectured behavior of the Hausdorff dimension of the limit set.
2026年11月30日(月)
15:30-17:00 数理科学研究科棟(駒場) 126 号室
紅村 冬大 氏 (九州工業大学)
Cartan-preserving *-automorphism groups: realization and obstructions for compact abelian groups
紅村 冬大 氏 (九州工業大学)
Cartan-preserving *-automorphism groups: realization and obstructions for compact abelian groups
[ 講演概要 ]
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年12月07日(月)
15:30-17:00 数理科学研究科棟(駒場) 126号室
宮川 明裕 氏 (京都大学)
TBA
宮川 明裕 氏 (京都大学)
TBA
2026年12月14日(月)
15:30-17:00 数理科学研究科棟(駒場) 126号室
荒野 悠輝 氏 (名古屋大学)
Prime actions of compact groups on von Neumann algebras
荒野 悠輝 氏 (名古屋大学)
Prime actions of compact groups on von Neumann algebras
2026年12月21日(月)
15:30-17:00 数理科学研究科棟(駒場) 126号室
小橋川 睦貴 氏 (東大数理)
TBA
小橋川 睦貴 氏 (東大数理)
TBA
2027年01月18日(月)
15:30-17:00 数理科学研究科棟(駒場) 126号室
藤江 克徳 氏 (愛知県立大学)
TBA
藤江 克徳 氏 (愛知県立大学)
TBA
2027年02月01日(月)
15:30-17:00 数理科学研究科棟(駒場) 126号室
Ikhan Choi 氏 (東大数理)
Analytic Kasparov product for non-separable C*-algebras
Ikhan Choi 氏 (東大数理)
Analytic Kasparov product for non-separable C*-algebras
