## Seminar information archive

Seminar information archive ～10/10｜Today's seminar 10/11 | Future seminars 10/12～

#### 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)

https://forms.gle/Uhy8uBujZatjNMsGA

**Hiroshi Fujiwara**(BroadBand Tower, Inc.)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 ]Explanation on the speedup technique of the classic computing and Innovation of causality in the root of the quantum computing

https://forms.gle/Uhy8uBujZatjNMsGA

### 2020/10/12

#### Seminar on Geometric Complex Analysis

10:30-12:00 Online

Two topics on psedoconvex domains (Japanese)

[ Reference URL ]

https://zoom.us/meeting/register/tJ0vcu2rrDIqG9Rv5AT0Mpi37urIkJ1IRldB

**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

An entropic proof of cutoff on Ramanujan graphs

[ Reference URL ]

https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

**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)

https://forms.gle/Uhy8uBujZatjNMsGA

**Hiroshi Fujiwara**(BroadBand Tower, Inc.)From a neural network to deep learning (Japanese)

[ Abstract ]

Explanation on how to reach from a neural network to deep learning

[ Reference URL ]Explanation on how to reach from a neural network to deep learning

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 ]

https://docs.google.com/forms/d/e/1FAIpQLSd7MT077191TeM4aQzeo2hK9Bqn6HQudr3pjLRdmEqND2heqQ/viewform?usp=sf_link

**( )**(Japanese)

[ Reference URL ]

https://docs.google.com/forms/d/e/1FAIpQLSd7MT077191TeM4aQzeo2hK9Bqn6HQudr3pjLRdmEqND2heqQ/viewform?usp=sf_link

### 2020/10/07

#### Mathematical Biology Seminar

16:00-17:00 Room # (Graduate School of Math. Sci. Bldg.)

The method of the third wave prediction of the infection by the Effective SIQR model (日本語)

**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.

The Atiyah-Patodi-Singer index of manifolds with boundary and domain-wall fermions (JAPANESE)

https://zoom.us/meeting/register/tJcqdO6pqz0pGNbwpZOpG-o2h4xJwmpma3zL

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 ]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.

https://zoom.us/meeting/register/tJcqdO6pqz0pGNbwpZOpG-o2h4xJwmpma3zL

### 2020/10/01

#### Information Mathematics Seminar

16:50-18:35 Online

From the Cyber Attack by the malware to the Zero Trust Network (Japanese)

https://forms.gle/Uhy8uBujZatjNMsGA

**Hiroshi Fujiwara**(BroadBand Tower, Inc.)From the Cyber Attack by the malware to the Zero Trust Network (Japanese)

[ Abstract ]

I explain the Cyber Attack by the malware and the Zero Trust Network.

[ Reference URL ]I explain the Cyber Attack by the malware and the Zero Trust Network.

https://forms.gle/Uhy8uBujZatjNMsGA

#### Operator Algebra Seminars

16:45-18:15 Online

A characterization of the Razak-Jacelon algebra

[ Reference URL ]

https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

**Norio Nawata**(Osaka Univ.)A characterization of the Razak-Jacelon algebra

[ Reference URL ]

https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

### 2020/09/29

#### Tuesday Seminar on Topology

17:00-18:00 Online

Pre-registration required. See our seminar webpage.

Witten-Reshetikhin-Turaev function for a knot in Seifert manifolds (JAPANESE)

https://zoom.us/meeting/register/tJcqdO6pqz0pGNbwpZOpG-o2h4xJwmpma3zL

Pre-registration required. See our seminar webpage.

**Kohei Iwaki**(The University of Tokyo)Witten-Reshetikhin-Turaev function for a knot in Seifert manifolds (JAPANESE)

[ Abstract ]

In 1998, Lawrence-Zagier introduced a certain q-series and proved that its limit value at root of unity q=exp(2π i / K) coincides with the SU(2) Witten-Reshetikhin-Turaev (WRT) invariant of the Poincare homology sphere Σ(2,3,5) at the level K. Employing the idea of Gukov-Marino-Putrov based on resurgent analysis, we generalize the result of Lawrence-Zagier for the Seifert loops (Seifert manifolds with a single loop inside). That is, for each Seifert loop, we introduce an explicit q-series (WRT function) and show that its limit value at the root of unity coincides with the WRT invariant of the Seifert loop. We will also discuss a q-difference equation satisfied by the WRT function. This talk is based on a joint work with H. Fuji, H. Murakami and Y. Terashima which is available on arXiv:2007.15872.

[ Reference URL ]In 1998, Lawrence-Zagier introduced a certain q-series and proved that its limit value at root of unity q=exp(2π i / K) coincides with the SU(2) Witten-Reshetikhin-Turaev (WRT) invariant of the Poincare homology sphere Σ(2,3,5) at the level K. Employing the idea of Gukov-Marino-Putrov based on resurgent analysis, we generalize the result of Lawrence-Zagier for the Seifert loops (Seifert manifolds with a single loop inside). That is, for each Seifert loop, we introduce an explicit q-series (WRT function) and show that its limit value at the root of unity coincides with the WRT invariant of the Seifert loop. We will also discuss a q-difference equation satisfied by the WRT function. This talk is based on a joint work with H. Fuji, H. Murakami and Y. Terashima which is available on arXiv:2007.15872.

https://zoom.us/meeting/register/tJcqdO6pqz0pGNbwpZOpG-o2h4xJwmpma3zL

### 2020/08/26

#### thesis presentations

16:00-17:15 Online

Irregular Riemann–Hilbert correspondence and its applications to Fourier transforms of holonomic D-modules

[ Reference URL ]

https://forms.gle/jfh9Hpyt3XZXXcft6

**ITO Yohei**(Graduate Scool of Mathematical Sciences University of tokyo)Irregular Riemann–Hilbert correspondence and its applications to Fourier transforms of holonomic D-modules

[ Reference URL ]

https://forms.gle/jfh9Hpyt3XZXXcft6

### 2020/07/31

#### thesis presentations

10:30-11:45 Online

Theory on Kähler metrics with constant exponentially weighted scalar curvature and exponentially weighted K-stability including Kähler-Ricci solitons

[ Reference URL ]

https://forms.gle/jfh9Hpyt3XZXXcft6

**INOUE Eiji**(Graduate Scool of Mathematical Sciences University of tokyo)Theory on Kähler metrics with constant exponentially weighted scalar curvature and exponentially weighted K-stability including Kähler-Ricci solitons

[ Reference URL ]

https://forms.gle/jfh9Hpyt3XZXXcft6

#### thesis presentations

13:15-14:30 Online

Studies on singular Hermitian metrics on holomorphic vector bundles via L² estimates and L² extension theorems

[ Reference URL ]

https://forms.gle/jfh9Hpyt3XZXXcft6

**INAYAMA Takahiro**(Graduate Scool of Mathematical Sciences University of tokyo)Studies on singular Hermitian metrics on holomorphic vector bundles via L² estimates and L² extension theorems

[ Reference URL ]

https://forms.gle/jfh9Hpyt3XZXXcft6

### 2020/07/30

#### thesis presentations

10:30-11:45 Online

Monopole Floer homology for codimension-3 Riemannian foliation

[ Reference URL ]

https://forms.gle/jfh9Hpyt3XZXXcft6

**LIN Dexie**(Graduate Scool of Mathematical Sciences University of tokyo)Monopole Floer homology for codimension-3 Riemannian foliation

[ Reference URL ]

https://forms.gle/jfh9Hpyt3XZXXcft6

### 2020/07/28

#### Tuesday Seminar on Topology

17:00-18:00 Online

Pre-registration required. See our seminar webpage.

A double filtration for the mapping class group and the Goeritz group of the sphere (ENGLISH)

https://zoom.us/webinar/register/WN_oS594Z6BRyaKNCvlm3yCoQ

Pre-registration required. See our seminar webpage.

**Anderson Vera**(RIMS, Kyoto University)A double filtration for the mapping class group and the Goeritz group of the sphere (ENGLISH)

[ Abstract ]

I will talk about a double-indexed filtration of the mapping class group and of the Goeritz group of the sphere, the latter is the group of isotopy classes of self-homeomorphisms of the 3-sphere which preserves the standard Heegaard splitting of $S^3$. In particular I will explain how this double filtration allows to write the Torelli group as a product of some subgroups of the mapping class group. A similar study could be done for the group of automorphisms of a free group. (work in progress with K. Habiro)

[ Reference URL ]I will talk about a double-indexed filtration of the mapping class group and of the Goeritz group of the sphere, the latter is the group of isotopy classes of self-homeomorphisms of the 3-sphere which preserves the standard Heegaard splitting of $S^3$. In particular I will explain how this double filtration allows to write the Torelli group as a product of some subgroups of the mapping class group. A similar study could be done for the group of automorphisms of a free group. (work in progress with K. Habiro)

https://zoom.us/webinar/register/WN_oS594Z6BRyaKNCvlm3yCoQ

#### thesis presentations

10:30-11:45 Online

Twisted arrow categories of operads and Segal conditions

[ Reference URL ]

https://forms.gle/jfh9Hpyt3XZXXcft6

**Brkin,Sergei Vladimirovich**(Graduate Scool of Mathematical Sciences University of tokyo)Twisted arrow categories of operads and Segal conditions

[ Reference URL ]

https://forms.gle/jfh9Hpyt3XZXXcft6

### 2020/07/21

#### Numerical Analysis Seminar

16:30-18:00 Online

Structure-preserving numerical schemes for constrained gradient flows of planar curves (Japanese)

[ Reference URL ]

https://forms.gle/3JiNEjWnrWLW8cFA9

**Tomoya Kemmochi**(Nagoya University)Structure-preserving numerical schemes for constrained gradient flows of planar curves (Japanese)

[ Reference URL ]

https://forms.gle/3JiNEjWnrWLW8cFA9

#### Tuesday Seminar on Topology

17:00-18:00 Online

Pre-registration required. See our seminar webpage.

Twisted arrow categories of operads and Segal conditions (ENGLISH)

https://zoom.us/webinar/register/WN_oS594Z6BRyaKNCvlm3yCoQ

Pre-registration required. See our seminar webpage.

**Sergei Burkin**(The University of Tokyo)Twisted arrow categories of operads and Segal conditions (ENGLISH)

[ Abstract ]

We generalize twisted arrow category construction from categories to operads, and show that several important categories, including the simplex category $\Delta$, Segal's category $\Gamma$ and Moerdijk--Weiss category $\Omega$ are twisted arrow categories of operads. Twisted arrow categories of operads are closely connected with Segal conditions, and the corresponding theory can be generalized from multi-object associative algebras (i.e. categories) to multi-object P-algebras for reasonably nice operads P.

[ Reference URL ]We generalize twisted arrow category construction from categories to operads, and show that several important categories, including the simplex category $\Delta$, Segal's category $\Gamma$ and Moerdijk--Weiss category $\Omega$ are twisted arrow categories of operads. Twisted arrow categories of operads are closely connected with Segal conditions, and the corresponding theory can be generalized from multi-object associative algebras (i.e. categories) to multi-object P-algebras for reasonably nice operads P.

https://zoom.us/webinar/register/WN_oS594Z6BRyaKNCvlm3yCoQ

#### Tuesday Seminar on Topology

18:00-19:00 Online

Pre-registration required. See our seminar webpage.

Monopole Floer homology for codimension-3 Riemannian foliation (ENGLISH)

https://zoom.us/webinar/register/WN_oS594Z6BRyaKNCvlm3yCoQ

Pre-registration required. See our seminar webpage.

**Dexie Lin**(The University of Tokyo)Monopole Floer homology for codimension-3 Riemannian foliation (ENGLISH)

[ Abstract ]

In this paper, we give a systematic study of Seiberg-Witten theory on closed oriented manifold with codimension-3 oriented Riemannian foliation. Under a certain topological condition, we construct the basic monopole Floer homologies for a transverse spinc structure with a bundle-like metric, generic perturbation and a complete local system. We will show that these homologies are independent of the bundle-like metric and generic perturbation. The major difference between the basic monopole Floer homologies and the ones on manifolds is the necessity to use the complete local system to construct the monopole Floer homologies.

[ Reference URL ]In this paper, we give a systematic study of Seiberg-Witten theory on closed oriented manifold with codimension-3 oriented Riemannian foliation. Under a certain topological condition, we construct the basic monopole Floer homologies for a transverse spinc structure with a bundle-like metric, generic perturbation and a complete local system. We will show that these homologies are independent of the bundle-like metric and generic perturbation. The major difference between the basic monopole Floer homologies and the ones on manifolds is the necessity to use the complete local system to construct the monopole Floer homologies.

https://zoom.us/webinar/register/WN_oS594Z6BRyaKNCvlm3yCoQ

### 2020/07/16

#### Operator Algebra Seminars

16:45-18:15 Online

Complex quantum groups and the Baum-Connes conjecture (English)

[ Reference URL ]

https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

**Christian Voigt**(Univ. Glasgow)Complex quantum groups and the Baum-Connes conjecture (English)

[ Reference URL ]

https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

#### Information Mathematics Seminar

16:50-18:35 Online

Basics of the speedup technique of the classic computing and Innovation of Causality in the root of the quantum computing (Japanese)

[学外用] https://docs.google.com/forms/d/1d1RWvV8j1TzXg8eF93zMZeIzJeIvdq9zY8htO8w2St0/ [学内用] https://bit.ly/2zCBj8x (g.ecc.u-tokyo.ac.jpアカウントでアクセスできます)

**HIroshi Fujiwara**(BroadBand Tower, Inc.)Basics of the speedup technique of the classic computing and Innovation of Causality in the root of the quantum computing (Japanese)

[ Abstract ]

Explanation of the speedup technique of the classic computing and innovation of causality in the root of the quantum computing

[ Reference URL ]Explanation of the speedup technique of the classic computing and innovation of causality in the root of the quantum computing

[学外用] https://docs.google.com/forms/d/1d1RWvV8j1TzXg8eF93zMZeIzJeIvdq9zY8htO8w2St0/ [学内用] https://bit.ly/2zCBj8x (g.ecc.u-tokyo.ac.jpアカウントでアクセスできます)

### 2020/07/14

#### Tuesday Seminar on Topology

17:30-18:30 Online

Joint with Lie Groups and Representation Theory Seminar. Pre-registration required. See our seminar webpage.

Kobayashi's properness criterion and totally geodesic submanifolds in locally symmetric spaces (JAPANESE)

https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html

Joint with Lie Groups and Representation Theory Seminar. Pre-registration required. See our seminar webpage.

**Takayuki Okuda**(Hiroshima University)Kobayashi's properness criterion and totally geodesic submanifolds in locally symmetric spaces (JAPANESE)

[ Abstract ]

Let G be a Lie group and X a homogeneous G-space. A discrete subgroup of G acting on X properly is called a discontinuous group for X. We are interested in constructions and classifications of discontinuous groups for a given X.

It is well-known that if the isotropies of G on X are compact, any closed subgroup acts on X properly. However, the cases where the isotropies are non-compact, the same claim does not hold in general.

Let us consider the case where G is a linear reductive. In this situation, T. Kobayashi [Math. Ann. (1989)], [J. Lie Theory (1996)]

gave a criterion for the properness of the action on a homogeneous G-space X of closed subgroups in G.

In this talk, we consider homogeneous G-spaces of reductive types realized as families of totally geodesic submanifolds in non-compact Riemannian symmetric spaces. As a main result, we give a translation of Kobayashi's criterion within the framework of Riemannian geometry. In particular, for a torsion-free discrete subgroup of G, the criterion can be stated in terms of totally geodesic submanifolds in the Riemannian locally symmetric space corresponding to the subgroup in G.

[ Reference URL ]Let G be a Lie group and X a homogeneous G-space. A discrete subgroup of G acting on X properly is called a discontinuous group for X. We are interested in constructions and classifications of discontinuous groups for a given X.

It is well-known that if the isotropies of G on X are compact, any closed subgroup acts on X properly. However, the cases where the isotropies are non-compact, the same claim does not hold in general.

Let us consider the case where G is a linear reductive. In this situation, T. Kobayashi [Math. Ann. (1989)], [J. Lie Theory (1996)]

gave a criterion for the properness of the action on a homogeneous G-space X of closed subgroups in G.

In this talk, we consider homogeneous G-spaces of reductive types realized as families of totally geodesic submanifolds in non-compact Riemannian symmetric spaces. As a main result, we give a translation of Kobayashi's criterion within the framework of Riemannian geometry. In particular, for a torsion-free discrete subgroup of G, the criterion can be stated in terms of totally geodesic submanifolds in the Riemannian locally symmetric space corresponding to the subgroup in G.

https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html

#### Lie Groups and Representation Theory

17:30-18:30 Room ## (Graduate School of Math. Sci. Bldg.)

Joint with Tuesday Seminar on Topology. Online.

Kobayashi's properness criterion and totally geodesic submanifolds in locally symmetric spaces (Japanese)

Joint with Tuesday Seminar on Topology. Online.

**Takayuki Okuda**(Hiroshima University)Kobayashi's properness criterion and totally geodesic submanifolds in locally symmetric spaces (Japanese)

[ Abstract ]

Let G be a Lie group and X a homogeneous G-space.

A discrete subgroup of G acting on X properly is called a discontinuous group for X.

We are interested in constructions and classifications of discontinuous groups for a given X.

It is well-known that if the isotropies of G on X are compact, any closed subgroup acts on X properly.

However, the cases where the isotropies are non-compact, the same claim does not hold in general.

Let us consider the case where G is a linear reductive.

In this situation, T. Kobayashi [Math. Ann. (1989)], [J. Lie Theory (1996)] gave a criterion for the properness of the action on a homogeneous G-space X of closed subgroups in G.

In this talk, we consider homogeneous G-spaces of reductive types realized as families of totally geodesic submanifolds in non-compact Riemannian symmetric spaces.

As a main result, we give a translation of Kobayashi's criterion within the framework of Riemannian geometry.

In particular, for a torsion-free discrete subgroup of G, the criterion can be stated in terms of totally geodesic submanifolds in the Riemannian locally symmetric space corresponding to the subgroup in G.

Let G be a Lie group and X a homogeneous G-space.

A discrete subgroup of G acting on X properly is called a discontinuous group for X.

We are interested in constructions and classifications of discontinuous groups for a given X.

It is well-known that if the isotropies of G on X are compact, any closed subgroup acts on X properly.

However, the cases where the isotropies are non-compact, the same claim does not hold in general.

Let us consider the case where G is a linear reductive.

In this situation, T. Kobayashi [Math. Ann. (1989)], [J. Lie Theory (1996)] gave a criterion for the properness of the action on a homogeneous G-space X of closed subgroups in G.

In this talk, we consider homogeneous G-spaces of reductive types realized as families of totally geodesic submanifolds in non-compact Riemannian symmetric spaces.

As a main result, we give a translation of Kobayashi's criterion within the framework of Riemannian geometry.

In particular, for a torsion-free discrete subgroup of G, the criterion can be stated in terms of totally geodesic submanifolds in the Riemannian locally symmetric space corresponding to the subgroup in G.

### 2020/07/13

#### Seminar on Geometric Complex Analysis

10:30-12:00 Online

$\mu$-cscK metrics and $\mu$K-stability of polarized manifolds

[ Reference URL ]

https://forms.gle/vSFPoVR6ugrkTGhX7

**INOUE Eiji**(University of Tokyo)$\mu$-cscK metrics and $\mu$K-stability of polarized manifolds

[ Reference URL ]

https://forms.gle/vSFPoVR6ugrkTGhX7

### 2020/07/09

#### Operator Algebra Seminars

16:45-18:15 Online

Affine isometric actions of groups on $L_p$-spaces : dependence on the value of $p$ (English)

[ Reference URL ]

https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

**Amine Marrakchi**(ENS Lyon)Affine isometric actions of groups on $L_p$-spaces : dependence on the value of $p$ (English)

[ Reference URL ]

https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

< Previous 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189 Next >