Seminar information archive

Seminar information archive ~05/21Today's seminar 05/22 | Future seminars 05/23~

2021/12/21

Tuesday Seminar on Topology

17:30-18:30   Online
Joint with Lie Groups and Representation Theory Seminar. See our seminar webpage.
Hiroki Shimakura (Tohoku University)
Classification of holomorphic vertex operator algebras of central charge 24 (JAPANESE)
[ Abstract ]
Holomorphic vertex operator algebras are imporant in vertex operator algebra theory. For example, the famous moonshine vertex operator algebra is holomorphic. One of the fundamental problems is to classify holomorphic vertex operator algebras. It is known that holomorphic vertex operator algebras of central charge 8 and 16 are lattice vertex operator algebras. I will talk about recent progress on the classification of holomorphic vertex operator algebras of central charge 24.
[ Reference URL ]
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html

Operator Algebra Seminars

16:45-18:15   Online
Wojciech Dybalski (Adam Mickiewicz University in Poznan)
Interacting massless infraparticles in 1+1 dimensions
(English)
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

Lie Groups and Representation Theory

17:30-18:30   Room #on line (Graduate School of Math. Sci. Bldg.)
Joint with Tuesday Seminar on Topology.
Hiroki Shimakura (Tohoku University)
Classification of holomorphic vertex operator algebras of central charge 24
(Japanese)
[ Abstract ]
Holomorphic vertex operator algebras are important in vertex operator algebra theory. For example, the famous moonshine vertex operator algebra is holomorphic.
One of the fundamental problems is to classify holomorphic vertex operator algebras. It is known that holomorphic vertex operator algebras of central charge 8 and 16 are lattice vertex operator algebras.
I will talk about recent progress on the classification of holomorphic vertex operator algebras of central charge 24.

2021/12/17

Colloquium

15:30-16:30   Online
Registration is closed (12:00, December 17).
Jun-Muk Hwang (Center for Complex Geometry, IBS, Korea)
Growth vectors of distributions and lines on projective hypersurfaces (ENGLISH)
[ Abstract ]
For a distribution on a manifold, its growth vector is a finite sequence of integers measuring the dimensions of the directions spanned by successive Lie brackets of local vector fields belonging to the distribution. The growth vector is the most basic invariant of a distribution, but it is sometimes hard to compute. As an example, we discuss natural distributions on the spaces of lines covering hypersurfaces of low degrees in the complex projective space. We explain the ideas in a joint work with Qifeng Li where the growth vector is determined for lines on a general hypersurface of degree 4 and dimension 5.

2021/12/16

Applied Analysis

16:00-17:00   Online
Zhanpeisov Erbol ( )
Existence of solutions for fractional semilinear parabolic equations in Besov-Morrey spaces (Japanese)
[ Reference URL ]
https://forms.gle/whpkgAwYvyQKQMzM8

Tokyo-Nagoya Algebra Seminar

16:45-18:15   Online
Please see the URL below for details on the online seminar.
Nicholas Williams (University of Cologne)
Cyclic polytopes and higher Auslander-Reiten theory (English)
[ Abstract ]
Oppermann and Thomas show that tilting modules over Iyama’s higher Auslander algebras of type A are in bijection with triangulations of even-dimensional cyclic polytopes. Triangulations of cyclic polytopes are partially ordered in two natural ways known as the higher Stasheff-Tamari orders, which were introduced in the 1990s by Kapranov, Voevodsky, Edelman, and Reiner as higher-dimensional generalisations of the Tamari lattice. These two partial orders were conjectured to be equal in 1996 by Edelman and Reiner, and we prove that this conjecture is true. We further show how the higher Stasheff-Tamari orders correspond in even dimensions to natural orders on tilting modules which were studied by Riedtmann, Schofield, Happel, and Unger. This then allows us to complete the picture of Oppermann and Thomas by showing that triangulations of odd-dimensional cyclic polytopes correspond to equivalence classes of d-maximal green sequences, which we introduce as higher-dimensional analogues of Keller’s maximal green sequences. We show that the higher Stasheff-Tamari orders correspond to natural orders on equivalence classes of d-maximal green sequences, which relate to the no-gap conjecture of Brustle, Dupont, and Perotin. The equality of the higher Stasheff-Tamari orders then implies that these algebraic orders on tilting modules and d-maximal green sequences are equal. If time permits, we will also discuss some results on mutation of cluster-tilting objects and triangulations.
[ Reference URL ]
http://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html

Information Mathematics Seminar

16:50-18:35   Online
Hiroshi Fujiwara (BroadBand Tower, Inc.)
The cyber attack to a car company supply chain network and Zero trust by the Cisco Systems (Japanese)
[ Abstract ]
Explanation on the cyber attack to the supply chain network of car company and zero trust by the Cisco Systems
[ Reference URL ]
https://docs.google.com/forms/d/1I3XD63V937BT_IoqRWBVN67goQAtbkSoIKs-6hfLUAM

2021/12/15

Seminar on Probability and Statistics

14:30-16:00   Room # (Graduate School of Math. Sci. Bldg.)
Estate Khmaladze (Victoria University of Wellington)
Theory of Distribution-free Testing
[ Abstract ]
Asia-Pacific Seminar in Probability and Statistics (APSPS)
https://sites.google.com/view/apsps/home

The aim of the talk is to introduce transformations of empirical-type processes by a group of unitary operators. Recall that if v_{nP} is empirical process on real line, based on a sample from P, it can be mapped into empirical process v_{nQ} by appropriate change of time

v_{nP}(h(x))=v_{nQ}(x)

where h(x) is continuous and increasing. This is the basis for distribution-free theory of goodness of fit testing. If w(\phi) is a function-parametric “empirical-type” process (i.e. has functions \phi from a space L as a time) and if K* is a unitary operator on L, then transformed process Kw we define as
Kw(\phi) = w(K*\phi)

These two formulas have good similarity, but one transformation in on the real line, while the other transformation in on functional space.This later one turns out to be of very broad use, and allows to base distribution-free theory upon it. Examples, we have specific results for, are parametric empirical
processes in R^d, regression empirical processes, those in GLM, parametric models for point processes and for Markov processes in discrete time. Hopefully, further examples will follow.
[ Reference URL ]
https://docs.google.com/forms/d/e/1FAIpQLSdFj1XF8WJSPRmE0GFKY2QxscaGxC9msM6GkEsAf0TgD9yv2g/viewform

2021/12/14

Operator Algebra Seminars

16:45-18:15   Online
Karen Strung (Czech Academy of Science)
Constructions in minimal amenable dynamics and applications to classification of $C^*$-algebras


[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

Lie Groups and Representation Theory

17:00-18:00   Room #on line (Graduate School of Math. Sci. Bldg.)
Yosuke Morita (Kyoto University)
On the definition of Conley indices (Japanese)
[ Abstract ]
Conley indices are used to describe local behaviour of topological dynamical systems. In this talk, I will explain a new framework for Conley index theory. Our approach is very elementary, and uses only general topology and some computations of inclusion relations of subsets.

2021/12/13

Seminar on Geometric Complex Analysis

10:30-12:00   Online
Masaya Kawamura (National Institute of Technology)
A generalized Hermitian curvature flow on almost Hermitian manifolds (Japanese)
[ Abstract ]
It is well-known that the Uniformization theorem (any Riemannian metric on a closed 2-manifold is conformal to one of constant curvature) can be proven by using the Ricci flow. J. Streets and G. Tian questioned whether or not a geometric flow can be used to classify non-Kähler complex surfaces as in the case of the Ricci flow. Also they asked if it is possible to prove classification results in higher dimensions by using geometric flows in non-Kähler Hermitian geometry. Streets and Tian considered that these flows should be close to the Kähler-Ricci flow as much as possible. From this point of view, they introduced a geometric flow called the Hermitian curvature flow (HCF) which evolves an initial Hermitian metric in the direction of a Ricci-type tensor of the Chern connection modified with some lower order torsion terms. Streets and Tian also introduced another geometric flow, which is called the pluriclosed flow (PCF), by choosing torsion terms to preserve the pluriclosed condition on Hermitian metrics. Y. Ustinovskiy studied a particular version of the HCF over a compact Hermitian manifold. Ustinovskiy proved that if the initial metric has Griffiths positive (non-negative) Chern curvature, then this property is preserved along the flow.

In recent years, some results concerning geometric flows on complex manifolds have been extended to the almost complex setting. For instance, L. Vezzoni defined a new Hermitian curvature flow on almost Hermitian manifolds for generalizing some studies on the HCF and the Hermitian Hilbert functional. And J. Chu, V. Tosatti and B. Weinkove considered parabolic Monge-Ampère equation on almost Hermitian manifolds, which is equivalent to the almost complex Chern-Ricci flow. T. Zheng characterized the maximal existence time for a solution to the almost complex Chern-Ricci flow.

In this talk, we consider a generalized Hermitian curvature flow in almost Hermitian geometry and introduce that it has some properties such as the long-time existence obstruction, the uniform equivalence between its solution and an almost Hermitian metric, and the preservation result along the flow.
[ Reference URL ]
https://u-tokyo-ac-jp.zoom.us/meeting/register/tJ0vcu2rrDIqG9Rv5AT0Mpi37urIkJ1IRldB

2021/12/09

Information Mathematics Seminar

16:50-18:35   Online
Hiroshi Fujiwara (BroadBand Tower, Inc.)
The consideration of the account injustice access case and zero trust by Microsoft (Japanese)
[ Abstract ]
The explanation on the account injustice access case and zero trust by Microsoft
[ Reference URL ]
https://docs.google.com/forms/d/1I3XD63V937BT_IoqRWBVN67goQAtbkSoIKs-6hfLUAM

2021/12/07

Operator Algebra Seminars

16:45-18:15   Online
Junichiro Matsuda (Kyoto Univ.)
Classification of quantum graphs on $M_2$ and their quantum automorphism groups
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

Tuesday Seminar on Topology

17:00-1800   Online
Pre-registration required. See our seminar webpage.
Taketo Sano (The Univesity of Tokyo)
A Bar-Natan homotopy type (JAPANESE)
[ Abstract ]
In year 2000, Khovanov introduced a categorification of the Jones polynomial, now known as Khovanov homology. In 2014, Lipshitz and Sarkar introduced a spatial refinement of Khovanov homology, called Khovanov homotopy type, which is a finite CW spectrum whose reduced cellular cohomology recovers Khovanov homology. On the algebraic level, there are several deformations of Khovanov homology, such as Lee homology and Bar-Natan homology. These variants are also important in that they give knot invariants such as Rasmussen’s $s$-invariant. Whether these variants admit spatial refinements have been open.

In 2021, the speaker constructed a spatial refinement of Bar-Natan homology and determined its stable homotopy type. The construction follows that of Lipshitz and Sarkar, which is based on the construction proposed by Cohen, Segal and Jones using the concept of flow categories. Also, we adopt techniques called “Morse moves in flow categories” introduced by Lobb et.al. to determine the stable homotopy type. Spacialy (or homotopically) refining the $s$-invariant is left as a future work.
[ Reference URL ]
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html

Lie Groups and Representation Theory

17:00-18:00   Room #on line (Graduate School of Math. Sci. Bldg.)
Toshihisa Kubo (Ryukoku University)
On the classification of the $K$-type formulas for the Heisenberg ultrahyperbolic equation (Japanese)
[ Abstract ]
About ten years ago, Kable constructed a one-parameter family $\square^{(n)}_s$ ($s\in \mathbb{C}$) of differential operators for $\mathfrak{sl}(n,\mathbb{C})$. He referred to $\square^{(n)}_s$ as the Heisenberg ultrahyperbolic operator. In the viewpoint of intertwining operators, $\square^{(n)}_s$ can be thought of as an intertwining differential operator between certain parabolically induced representations for $\widetilde{SL}(n,\mathbb{R})$. In this talk we discuss about the classification of the $K$-type formulas of the space of $K$-finite solutions to the differential equation $\square^{(3)}_sf=0$ for $\widetilde{SL}(3,\mathbb{R})$ and some related topics. This is joint work with Bent {\O}rsted.

2021/12/02

Information Mathematics Seminar

16:50-18:35   Online
Hiroshi Fujiwara (BroadBand Tower, Inc.)
The whole summary and other machine learning technique in the AI
~ LSTM/GAN/Unsupervised learning /Auto Encoder~ (Japanese)
[ Abstract ]
The whole summary and the explanation on other machine learning techniques in the AI (LSTM/GAN/Unsupervised learning /Auto Encoder).
[ Reference URL ]
https://docs.google.com/forms/d/1I3XD63V937BT_IoqRWBVN67goQAtbkSoIKs-6hfLUAM

Applied Analysis

16:00-17:00   Online

( )

[ Reference URL ]
https://forms.gle/6cKyu9meCxSv72N19

2021/11/30

Operator Algebra Seminars

16:45-18:15   Online
Yosuke Kubota (Shinshu Univ.)
Crystallographic $T$-duality in twisted equivariant $K$-theory
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

Tuesday Seminar on Topology

17:00-18:00   Online
Pre-registration required. See our seminar webpage.
Masatoshi Sato (Tokyo Denki University)
A non-commutative Reidemeister-Turaev torsion of homology cylinders (JAPANESE)
[ Abstract ]
The Reidemeister-Turaev torsion of homology cylinders takes values in the integral group ring of the first homology of a surface. We lift it to a torsion valued in the $K_1$-group of the completed rational group ring of the fundamental group of the surface. We show that it induces a finite type invariant of homology cylinders, and describe the induced map on the graded quotient of the Y-filtration of homology cylinders via the 1-loop part of the LMO functor and the Enomoto-Satoh trace. This talk is based on joint work with Yuta Nozaki and Masaaki Suzuki.
[ Reference URL ]
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html

Mathematical Biology Seminar

15:30-17:00   Room #オンライン開催 (Graduate School of Math. Sci. Bldg.)
Takeshi OJIMA (Fukushima University)
Endogenous Waves in a SIR Model with Risk Heterogeneity
(Japanese)
[ Reference URL ]
オンライン開催です.参加希望者は inaba@ms.u-tokyo.ac.jp までご連絡ください.

Lie Groups and Representation Theory

17:00-18:00   Room #on line (Graduate School of Math. Sci. Bldg.)
Quentin Labriet (Reims University)
Branching problems for conformal Lie groups and orthogonal polynomials (English)
[ Abstract ]
In this talk, I will present some results obtained during my PhD about a link between branching problems for conformal Lie groups and orthogonal polynomials. More precisely, I am going to look at some examples of branching problems for representations in the scalar-valued holomorphic discrete series of some conformal Lie groups. Using the geometry of symmetric cone, I will explain how the theory of orthogonal polynomials can be related to branching problems and to the construction of symmetry breaking and holographic operators.

2021/11/29

Seminar on Geometric Complex Analysis

10:30-12:00   Online
Akira Kitaoka (The University of Tokyo)
レンズ空間上のRay-Singer捩率とRumin複体のラプラシアン (Japanese)
[ Abstract ]
Rumin複体は、接触多様体に関するBernstein-Gelfand-Gelfand複体(BGG複体)である。BGG複体は、放物型幾何やフィルター付き多様体に対して構成される複体であり、BGG複体のコホモロジーはde Rhamコホモロジーに一致するという事が挙げられる。また、Rumin複体はsub-Riemmann極限を考えた際に自然に現れるという性質を持つ。

De Rham複体を使って定義した概念をRumin複体に置き換えるとどうなるのか、ということを考える。本講演では、この考えを解析的捩率に適応した場合を話す。レンズ空間上のユニモジュラーなホロのミーから誘導される平坦ベクトル束に対して、Rumin複体の解析的捩率の値が、Betti数とRay-Singer捩率を用いて表されることを報告する。
[ Reference URL ]
https://u-tokyo-ac-jp.zoom.us/meeting/register/tJ0vcu2rrDIqG9Rv5AT0Mpi37urIkJ1IRldB

2021/11/26

Colloquium

15:30-16:30   Online
Registration is closed (12:00, November 26).
Gang Tian (BICMR, Peking University)
Ricci flow on Fano manifolds (ENGLISH)
[ Abstract ]
Ricci flow was introduced by Hamilton in early 80s. It preserves the Kahlerian structure and has found many applications in Kahler geometry. In this expository talk, I will focus on Ricci flow on Fano manifolds. I will first survey some results in recent years, then I will discuss my joint work with Li and Zhu. I will also discuss the connection between the long time behavior of Ricci flow and some algebraic geometric problems for Fano manifolds.

Mathematical Biology Seminar

15:00-16:30   Online
Shinji NAKAOKA (Faculty of Advanced Life Science, Hokkaido University)
Derivation of structured population models of cellular proliferation on an
energy landscape
[ Reference URL ]
オンライン参加希望の方は,inaba@ms.u-tokyo.ac.jp までご連絡ください.

2021/11/25

Applied Analysis

16:00-17:30   Online
( )
(日本語)
[ Reference URL ]
https://forms.gle/xBAgncTERzYfauJE6

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