## Seminar information archive

### 2020/11/09

#### Seminar on Geometric Complex Analysis

10:30-12:00   Online
NOSE Toshihiro (Fukuoka Institute of Technology)
Meromorphic continuation of local zeta functions and nonpolar singularities
[ Reference URL ]
https://zoom.us/meeting/register/tJ0vcu2rrDIqG9Rv5AT0Mpi37urIkJ1IRldB

### 2020/11/05

#### Operator Algebra Seminars

16:45-18:15   Online
Zhengwei Liu (Tsinghua University)
Subfactors and Quantum Fourier Analysis (English)
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

#### Applied Analysis

16:00-17:30   Room #オンライン開催 (Graduate School of Math. Sci. Bldg.)
( )
Hölder gradient estimates on L^p-viscosity solutions of fully nonlinear parabolic equations with VMO coefficients (Japanese)
[ Abstract ]
We discuss fully nonlinear second-order uniformly parabolic equations, including parabolic Isaacs equations. Isaacs equations arise in the theory of stochastic differential games. In 2014, N.V. Krylov proved the existence of L^p-viscosity solutions of boundary value problems for equations with VMO (vanishing mean oscillation) “coefficients” when p>n+2. Furthermore, the solutions were in the parabolic Hölder space C^{1,α} for 0<α<1. Our purpose is to show C^{1,α} estimates on L^p-viscosity solutions of fully nonlinear parabolic equations under the same conditions as in Krylov’s result.
[ Reference URL ]

#### Information Mathematics Seminar

16:50-18:35   Online
History of PC rise and fall /What is a parallel processing? What is a
quantum gate? (Japanese)
[ Abstract ]
Explanation of the history of PC rise and fall, and also of a parallel processing and a quantum gate.
[ Reference URL ]
https://forms.gle/Uhy8uBujZatjNMsGA

### 2020/10/29

#### Operator Algebra Seminars

15:30-17:00   Online
Yoh Tanimoto (University of Rome, Tor Vergata)
Continuum (free) fields from lattice wavelet renormalization
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

#### Information Mathematics Seminar

16:50-18:35   Online
Supervised/Unsupervised Learning and Reinforcement Learning for Deep
Learning (Japanese)
[ Abstract ]
Explanation on supervised/unsupervised learning and reinforcement learning for deep
learning
[ Reference URL ]
https://forms.gle/Uhy8uBujZatjNMsGA

### 2020/10/27

#### Numerical Analysis Seminar

16:30-18:00   Online
Buyang Li (The Hong Kong Polytechnic University)
Convergent evolving finite element algorithms for mean curvature flow and Willmore flow of closed surfaces (English)
[ Abstract ]
We construct evolving surface finite element methods for the mean curvature and Willmore flow through equivalently reformulating the original equations into coupled systems governing the evolution of surface position, velocity, normal vector and mean curvature. Then we prove $H^1$-norm convergence of the proposed evolving surface finite element methods for the reformulated systems, by combining stability estimates and consistency estimates. The stability analysis is based on the matrix–vector formulation of the finite element method and does not use geometric arguments. The geometry enters only into the consistency estimates. Numerical experiments illustrate and complement the theoretical results.
[1] https://doi.org/10.1007/s00211-019-01074-2
[2] https://arxiv.org/abs/2007.15257
[ Reference URL ]
https://forms.gle/HeuUxWLGa696KPvz8

#### PDE Real Analysis Seminar

10:30-11:30   Room #　Zoomによるオンライン開催　 (Graduate School of Math. Sci. Bldg.)
Son Tu (University of Wisconsin Madison)
Vanishing discount problems for Hamilton-Jacobi equations on changing domains (English)
[ Abstract ]
We study the asymptotic behavior, as the discount factor vanishes, of the Hamilton-Jacobi equation with state-constraint on changing domains. Surprisingly, we can obtain both convergence results and non-convergence results in this convex setting. Moreover, we provide a very first result on the asymptotic expansion of the additive eigenvalue of the Hamiltonian with respect to the changing domains. The main tool we use is a duality representation of solution with viscosity Mather measures.

#### Tuesday Seminar on Topology

17:00-18:00   Online
Pre-registration required. See our seminar webpage.
Jun Yoshida (The University of Tokyo)
Vassiliev derivatives of Khovanov homology and its application (JAPANESE)
[ Abstract ]
Khovanov homology is a categorification of the Jones polynomial. It is known that Khovanov homology also arises from a categorical representation of braid groups, so we can regard it as a kind of quantum knot invariant. However, in contrast to the case of classical quantum invariants, its relation to Vassiliev invariants remains unclear. In this talk, aiming at the problem, we discuss a categorified version of Vassiliev skein relation on Khovanov homology. Namely, we extend Khovanov homology to singular links so that extended ones can be seen as "derivatives" in view of Vassiliev theory. As an application, we compute first derivatives to determine Khovanov homologies of twist knots. This talk is based on papers arXiv:2005.12664 (joint work with N.Ito) and arXiv:2007.15867.
[ Reference URL ]
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html

#### Tokyo-Nagoya Algebra Seminar

16:30-18:00   Online
Please see the URL below for details on the online seminar.
Yasuaki Gyoda (Nagoya University)
Positive cluster complex and $\tau$-tilting complex (Japanese)
[ Abstract ]
In cluster algebra theory, cluster complexes are actively studied as simplicial complexes, which represent the structure of a seed and its mutations. In this talk, I will discuss a certain subcomplex, called positive cluster complex, of a cluster complex. This is a subcomplex whose vertex set consists of all cluster variables except for those in the initial seed. I will also introduce another simplicial complex in this talk - the tau-tilting complex, which has vertices given by all indecomposable tau-rigid modules, and simplices given by basic tau-rigid modules. In the case of a cluster-tilted algebra, it turns out that a tau-tilting complex corresponds to some positive cluster complex. Due to this fact, we can investigate the structure of a tau-tilting complex of tau-tilting finite type by using the tools of cluster algebra theory. This is joint work with Haruhisa Enomoto.

### 2020/10/26

#### Seminar on Geometric Complex Analysis

10:30-12:00   Online
HATTORI Kota (Keio University)
Spectral convergence in geometric quantization
[ Reference URL ]
https://zoom.us/meeting/register/tJ0vcu2rrDIqG9Rv5AT0Mpi37urIkJ1IRldB

### 2020/10/22

#### Operator Algebra Seminars

16:45-18:15   Online
Hiroyasu Hamada (National Institute of Technology, Sasebo College)
$C^*$-algebras generated by multiplication operators and composition operators by functions with self-similar branches
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

#### Information Mathematics Seminar

16:50-18:35   Room #オンライン(Zoom) (Graduate School of Math. Sci. Bldg.)
Think about a zero trust from information security 10 size menace 2020 (Japanese)
[ Abstract ]
In this talk, we think about a zero trust from information security 10 size menace 2020.
[ Reference URL ]
https://forms.gle/Uhy8uBujZatjNMsGA

### 2020/10/20

#### Tuesday Seminar on Topology

17:00-18:00   Online
Pre-registration required. See our seminar webpage.
Alexandru Oancea (Sorbonne Université)
[ Abstract ]
A certain number of dualities between homological and cohomological invariants of free loop spaces have been observed over the years, having the flavour of Poincaré duality but nevertheless holding in an infinite dimensional setting. The goal of the talk will be to explain these through a new duality theorem, whose proof uses symplectic methods. The talk will report on joint work with Kai Cieliebak and Nancy Hingston.
[ Reference URL ]
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html

### 2020/10/19

#### Seminar on Geometric Complex Analysis

10:30-12:00   Online
MATSUMURA, Shin-ichi (Tohoku University)
On projective manifolds with pseudo-effective tangent bundle
[ Abstract ]
In this talk, I would like to discuss projective manifolds whose tangent bundle is pseudo-effective or admits a positively curved singular metric. I will explain a structure theorem for such manifolds and the classification in the two-dimensional case, comparing our theory with classical results for nef tangent bundle or non-negative bisectional curvature. Related open problems will be discussed if time permits.
This is joint work with Genki Hosono (Tohoku University) and Masataka Iwai (Osaka City University).
[ Reference URL ]
https://zoom.us/meeting/register/tJ0vcu2rrDIqG9Rv5AT0Mpi37urIkJ1IRldB

#### Seminar on Probability and Statistics

10:30-11:30   Room #Zoom (Graduate School of Math. Sci. Bldg.)
Yuta Koike (University of Tokyo)
Development of high-dimensional CLTs arising from high-frequency data analysis (日本語)
[ Reference URL ]

### 2020/10/15

#### Operator Algebra Seminars

16:45-18:15   Online
Sven Raum (Stockholm Univ.)
Structure of Hecke von Neumann algebras and applications to representation theory
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

#### Information Mathematics Seminar

16:50-18:35   Room #オンライン(Zoom) (Graduate School of Math. Sci. Bldg.)
Basics of the speedup technique of the classic computing and Innovation of Causality in the root of the quantum computing (Japanese)
[ Abstract ]
Explanation on the speedup technique of the classic computing and Innovation of causality in the root of the quantum computing
[ Reference URL ]
https://forms.gle/Uhy8uBujZatjNMsGA

### 2020/10/12

#### Seminar on Geometric Complex Analysis

10:30-12:00   Online
NOGUCHI Junjiro (University of Tokyo)
Two topics on psedoconvex domains (Japanese)
[ Reference URL ]
https://zoom.us/meeting/register/tJ0vcu2rrDIqG9Rv5AT0Mpi37urIkJ1IRldB

### 2020/10/08

#### Operator Algebra Seminars

16:45-18:15   Online
Narutaka Ozawa (RIMS, Kyoto Univ.)
An entropic proof of cutoff on Ramanujan graphs
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

#### Information Mathematics Seminar

16:50-18:35   Online
From a neural network to deep learning (Japanese)
[ Abstract ]
Explanation on how to reach from a neural network to deep learning
[ Reference URL ]
https://forms.gle/Uhy8uBujZatjNMsGA

#### Applied Analysis

16:00-17:30   Room #オンライン開催 (Graduate School of Math. Sci. Bldg.)
( )
(Japanese)
[ Reference URL ]

### 2020/10/07

#### Mathematical Biology Seminar

16:00-17:00   Room # (Graduate School of Math. Sci. Bldg.)
Masao Namiki (Former Executive Vice President, Board of Directors and Representative Executive Officers)
The method of the third wave prediction of the infection by the Effective SIQR model (日本語)

### 2020/10/06

#### Tuesday Seminar on Topology

17:30-18:30   Online
Pre-registration required. See our seminar webpage.
Shinichiroh Matsuo (Nagoya University)
The Atiyah-Patodi-Singer index of manifolds with boundary and domain-wall fermions (JAPANESE)
[ Abstract ]
We introduce a mathematician-friendly formulation of the physicist-friendly derivation of the Atiyah-Patodi-Singer index.

In a previous work, motivated by the study of lattice gauge theory, we derived a formula expressing the Atiyah-Patodi-Singer index in terms of the eta invariant of “domain-wall fermion Dirac operators” when the base manifold is a flat 4-dimensional torus. Now we generalise this formula to any even dimensional closed Riemannian manifolds, and prove it mathematically rigorously. Our proof uses a Witten localisation argument combined with a devised embedding into a cylinder of one dimension higher. Our viewpoint sheds some new light on the interplay among the Atiyah-Patodi-Singer boundary condition, domain-wall fermions, and edge modes.

This talk is based on a joint paper arXiv:1910.01987, to appear in CMP, with H. Fukaya, M. Furuta, T. Onogi, S. Yamaguchi, and M. Yamashita.
[ Reference URL ]
https://zoom.us/meeting/register/tJcqdO6pqz0pGNbwpZOpG-o2h4xJwmpma3zL

### 2020/10/01

#### Information Mathematics Seminar

16:50-18:35   Online