## Seminar information archive

Seminar information archive ～02/22｜Today's seminar 02/23 | Future seminars 02/24～

### 2012/01/31

#### Tuesday Seminar of Analysis

16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Obstacle problems in unbounded domains (ENGLISH)

**Michel Chipot**(University of Zurich)Obstacle problems in unbounded domains (ENGLISH)

[ Abstract ]

We will present a formulation of obstacle problems in unbounded

domains when the energy method does not work, i.e. whenthe force does not belong to H^{-1}.

We will present a formulation of obstacle problems in unbounded

domains when the energy method does not work, i.e. whenthe force does not belong to H^{-1}.

### 2012/01/30

#### Algebraic Geometry Seminar

15:30-17:00 Room #122 (Graduate School of Math. Sci. Bldg.)

On varieties of globally F-regular type (JAPANESE)

**Yoshinori Gongyo**(University of Tokyo)On varieties of globally F-regular type (JAPANESE)

[ Abstract ]

I will talk about recent topics on varieties of globally F-regular type.

I will talk about recent topics on varieties of globally F-regular type.

#### Seminar on Geometric Complex Analysis

10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Differential equations as embedding obstructions and vanishing theorems (ENGLISH)

**Damian Brotbek**(University of Tokyo)Differential equations as embedding obstructions and vanishing theorems (ENGLISH)

[ Abstract ]

Given a smooth projective variety $X$ it is natural to wonder what is the smallest integer $N$ such that one can embed $X$ into $\mathbf{P}^N$. In this talk I will first recall what can be said for any smooth projective variety, then I will explain how the existence of some particular differential equations on $X$ yields obstructions to the existence of some projective embeddings.

Given a smooth projective variety $X$ it is natural to wonder what is the smallest integer $N$ such that one can embed $X$ into $\mathbf{P}^N$. In this talk I will first recall what can be said for any smooth projective variety, then I will explain how the existence of some particular differential equations on $X$ yields obstructions to the existence of some projective embeddings.

### 2012/01/27

#### Colloquium

16:30-17:30 Room #123 (Graduate School of Math. Sci. Bldg.)

On Topological Blow-up (JAPANESE)

**Taro YOSHINO**(Graduate School of Mathematical Sciences, University of Tokyo)On Topological Blow-up (JAPANESE)

[ Abstract ]

Topological blow-up is a method to understand non-Hausdorff spaces. We define an obstruction to Hausdorffness, and call it crack. By `blowing up' the points in crack, we can obtain better space.

Topological blow-up is a method to understand non-Hausdorff spaces. We define an obstruction to Hausdorffness, and call it crack. By `blowing up' the points in crack, we can obtain better space.

### 2012/01/26

#### Operator Algebra Seminars

16:30-18:00 Room #117 (Graduate School of Math. Sci. Bldg.)

The transverse fundamental class of linear foliations

on torus bundles over the circle (ENGLISH)

**Catherine Oikonomides**(Univ. Tokyo)The transverse fundamental class of linear foliations

on torus bundles over the circle (ENGLISH)

### 2012/01/24

#### Numerical Analysis Seminar

16:30-18:00 Room #002 (Graduate School of Math. Sci. Bldg.)

Phasefield model for crack simulation and its application (JAPANESE)

[ Reference URL ]

http://www.infsup.jp/utnas/

**Takeshi Takaishi**(Hiroshima Kokusai Gakuin University)Phasefield model for crack simulation and its application (JAPANESE)

[ Reference URL ]

http://www.infsup.jp/utnas/

### 2012/01/23

#### Algebraic Geometry Seminar

15:30-17:00 Room #122 (Graduate School of Math. Sci. Bldg.)

Sigularities and Kodaira dimension of the moduli of stable sheaves on Enriques surfaces (JAPANESE)

**Kimiko Yamada**(Okayama university)Sigularities and Kodaira dimension of the moduli of stable sheaves on Enriques surfaces (JAPANESE)

[ Abstract ]

We shall estimate singularities of moduli of stable sheaves on Enriques/hyper-elliptic surfaces via the Kuranishi theory, consider when its singularities are canonical, and calculate its Kodaira dimension.

We shall estimate singularities of moduli of stable sheaves on Enriques/hyper-elliptic surfaces via the Kuranishi theory, consider when its singularities are canonical, and calculate its Kodaira dimension.

#### Seminar on Geometric Complex Analysis

10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Twistor correspondence for R-invariant indefinite self-dual metric on R^4 (JAPANESE)

**Fuminori Nakata**(Tokyo University of Science)Twistor correspondence for R-invariant indefinite self-dual metric on R^4 (JAPANESE)

#### GCOE lecture series

13:30-15:00 Room #122 (Graduate School of Math. Sci. Bldg.)

TBA(中止になりました) (ENGLISH)

**Mihai Paun**(Institut Élie Cartan and KIAS)TBA(中止になりました) (ENGLISH)

### 2012/01/20

#### Kavli IPMU Komaba Seminar

14:45-16:15 Room #056 (Graduate School of Math. Sci. Bldg.)

Refined holomorphic anomaly equations (ENGLISH)

**Albrecht Klemm**(The University of Bonn)Refined holomorphic anomaly equations (ENGLISH)

[ Abstract ]

We propose a derivation of refined holomophic

anomaly equation from the word-sheet point of

view and discuss the interpretation of the

refined BPS invariants for local Calabi-Yau

spaces.

We propose a derivation of refined holomophic

anomaly equation from the word-sheet point of

view and discuss the interpretation of the

refined BPS invariants for local Calabi-Yau

spaces.

### 2012/01/19

#### Applied Analysis

16:00-17:30 Room #128 (Graduate School of Math. Sci. Bldg.)

Undercompressible shocks and moving phase boundaries

(ENGLISH)

**Philippe G. LeFloch**(Univ. Paris 6 / CNRS)Undercompressible shocks and moving phase boundaries

(ENGLISH)

[ Abstract ]

I will present a study of traveling wave solutions to third-order, diffusive-dispersive equations, which arise in the modeling of complex fluid flows and represent regularization-sensitive wave patterns, especially undercompressive shock waves and moving phase boundaries. The qualitative properties of these (possibly oscillatory) traveling waves are well-understood in terms of the so-called kinetic relation, and this has led to a new theory of (nonclassical) solutions to nonlinear hyperbolic systems. Relevant papers are available at the link: www.philippelefloch.org.

I will present a study of traveling wave solutions to third-order, diffusive-dispersive equations, which arise in the modeling of complex fluid flows and represent regularization-sensitive wave patterns, especially undercompressive shock waves and moving phase boundaries. The qualitative properties of these (possibly oscillatory) traveling waves are well-understood in terms of the so-called kinetic relation, and this has led to a new theory of (nonclassical) solutions to nonlinear hyperbolic systems. Relevant papers are available at the link: www.philippelefloch.org.

### 2012/01/18

#### GCOE lecture series

15:30-17:00 Room #122 (Graduate School of Math. Sci. Bldg.)

TBA(中止になりました) (ENGLISH)

**Mihai Paun**(Institut Élie Cartan and KIAS)TBA(中止になりました) (ENGLISH)

### 2012/01/17

#### Tuesday Seminar on Topology

16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)

On the Johnson cokernels of the mapping class group of a surface (joint work with Naoya Enomoto) (JAPANESE)

**Takao Satoh**(Tokyo University of Science)On the Johnson cokernels of the mapping class group of a surface (joint work with Naoya Enomoto) (JAPANESE)

[ Abstract ]

In general, the Johnson homomorphisms of the mapping class group of a surface are used to investigate graded quotients of the Johnson filtration of the mapping class group. These graded quotients are considered as a sequence of approximations of the Torelli group. Now, there is a broad range of remarkable results for the Johnson homomorphisms.

In this talk, we concentrate our focus on the cokernels of the Johnson homomorphisms of the mapping class group. By a work of Shigeyuki Morita and Hiroaki Nakamura, it is known that an Sp-irreducible module [k] appears in the cokernel of the k-th Johnson homomorphism with multiplicity one if k=2m+1 for any positive integer m. In general, however, to determine Sp-structure of the cokernel is quite a difficult preblem.

Our goal is to show that we have detected new irreducible components in the cokernels. More precisely, we will show that there appears an Sp-irreducible module [1^k] in the cokernel of the k-th Johnson homomorphism with multiplicity one if k=4m+1 for any positive integer m.

In general, the Johnson homomorphisms of the mapping class group of a surface are used to investigate graded quotients of the Johnson filtration of the mapping class group. These graded quotients are considered as a sequence of approximations of the Torelli group. Now, there is a broad range of remarkable results for the Johnson homomorphisms.

In this talk, we concentrate our focus on the cokernels of the Johnson homomorphisms of the mapping class group. By a work of Shigeyuki Morita and Hiroaki Nakamura, it is known that an Sp-irreducible module [k] appears in the cokernel of the k-th Johnson homomorphism with multiplicity one if k=2m+1 for any positive integer m. In general, however, to determine Sp-structure of the cokernel is quite a difficult preblem.

Our goal is to show that we have detected new irreducible components in the cokernels. More precisely, we will show that there appears an Sp-irreducible module [1^k] in the cokernel of the k-th Johnson homomorphism with multiplicity one if k=4m+1 for any positive integer m.

#### Numerical Analysis Seminar

17:00-18:00 Room #123 (Graduate School of Math. Sci. Bldg.)

Numerical computations of flow problems with the moving boundary by an area-preserving scheme (JAPANESE)

[ Reference URL ]

http://www.infsup.jp/utnas/

**Daisuke Tagami**(Kyushu University)Numerical computations of flow problems with the moving boundary by an area-preserving scheme (JAPANESE)

[ Reference URL ]

http://www.infsup.jp/utnas/

### 2012/01/16

#### Algebraic Geometry Seminar

15:30-17:00 Room #122 (Graduate School of Math. Sci. Bldg.)

TBA(Cancelled) (JAPANESE)

**Mihai Paun**(Institut Élie Cartan and KIAS)TBA(Cancelled) (JAPANESE)

#### Seminar on Geometric Complex Analysis

10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)

A ramification theorem for the ratio of canonical forms of flat surfaces in hyperbolic 3-space (JAPANESE)

**Yu Kawakami**(Yamaguchi University)A ramification theorem for the ratio of canonical forms of flat surfaces in hyperbolic 3-space (JAPANESE)

[ Abstract ]

We provide an effective ramification theorem for the ratio of canonical forms of weakly complete flat fronts in the hyperbolic 3-space. As an application, we give a simple proof of the classification of complete nonsingular flat surfaces in the hyperbolic 3-space.

We provide an effective ramification theorem for the ratio of canonical forms of weakly complete flat fronts in the hyperbolic 3-space. As an application, we give a simple proof of the classification of complete nonsingular flat surfaces in the hyperbolic 3-space.

#### Operator Algebra Seminars

16:30-18:00 Room #117 (Graduate School of Math. Sci. Bldg.)

Is an irng singly generated as an ideal? (JAPANESE)

**Narutaka Ozawa**(RIMS, Kyoto University)Is an irng singly generated as an ideal? (JAPANESE)

#### GCOE lecture series

15:30-17:00 Room #122 (Graduate School of Math. Sci. Bldg.)

TBA(中止になりました) (ENGLISH)

**Mihai Paun**(Institut Élie Cartan and KIAS)TBA(中止になりました) (ENGLISH)

### 2012/01/12

#### Number Theory Seminar

18:15-19:15 Room #056 (Graduate School of Math. Sci. Bldg.)

New perspectives on the Breuil-Mézard conjecture (joint with M. Emerton)

(ENGLISH)

**Toby Gee**(Imperial College London)New perspectives on the Breuil-Mézard conjecture (joint with M. Emerton)

(ENGLISH)

[ Abstract ]

I will discuss joint work with Matthew Emerton on geometric approaches to the Breuil-Mézard conjecture, generalising a geometric approach of Breuil and Mézard. I will discuss a proof of the geometric version of the original conjecture, as well as work in progress on a geometric version of the conjecture which does not make use of a fixed residual representation.

(本講演は「東京パリ数論幾何セミナー」として、インターネットによる東大数理とIHESとの双方向同時中継で行います。)

I will discuss joint work with Matthew Emerton on geometric approaches to the Breuil-Mézard conjecture, generalising a geometric approach of Breuil and Mézard. I will discuss a proof of the geometric version of the original conjecture, as well as work in progress on a geometric version of the conjecture which does not make use of a fixed residual representation.

(本講演は「東京パリ数論幾何セミナー」として、インターネットによる東大数理とIHESとの双方向同時中継で行います。)

### 2012/01/06

#### Operator Algebra Seminars

16:30-18:00 Room #118 (Graduate School of Math. Sci. Bldg.)

Diagrammatical methods in theory of subfactors (ENGLISH)

**Yasuyuki Kawahigashi**(Univ. Tokyo)Diagrammatical methods in theory of subfactors (ENGLISH)

### 2012/01/05

#### Operator Algebra Seminars

16:30-18:00 Room #117 (Graduate School of Math. Sci. Bldg.)

Classification and amenability in theory of von Neumann algebras (ENGLISH)

**Yasuyuki Kawahigashi**(Univ. Tokyo)Classification and amenability in theory of von Neumann algebras (ENGLISH)

### 2011/12/27

#### Operator Algebra Seminars

14:30-18:00 Room #117 (Graduate School of Math. Sci. Bldg.)

Deformation of algebras associated to group cocycles (JAPANESE)

Construction of wedge-local nets through

Longo-Witten endomorphisms (JAPANESE)

**Makoto Yamashita**(Universita di Roma "Tor Vergata") 14:30-16:00Deformation of algebras associated to group cocycles (JAPANESE)

**Yoh Tanimoto**(Universitaet Goettingen) 16:30-18:00Construction of wedge-local nets through

Longo-Witten endomorphisms (JAPANESE)

#### GCOE Seminars

13:30-14:30 Room #370 (Graduate School of Math. Sci. Bldg.)

The Modelling of Dislocations in the Early Stage of the Metal Fatigue (ENGLISH)

**Yichao Zhu**(University of Oxford)The Modelling of Dislocations in the Early Stage of the Metal Fatigue (ENGLISH)

[ Abstract ]

Understanding fatigue of metal under cyclic loads is crucial for some fields in mechanical engineering, such as the design of wheels of high speed trains and the aeroplane engine. Experimentally it has been found that this type of

fatigue is closely related to a ladder shape pattern of dislocations known as a persistent slip band (PSB) at a microscopic level. In this talk, a quantitative description for the formation of PSBs is proposed from two angles: 1. the motion of a single dislocation analysed by using asymptotic expansions and numerical simulations; 2. the collective behaviour of a large number of dislocations analysed by using a method of multiple scales.

Understanding fatigue of metal under cyclic loads is crucial for some fields in mechanical engineering, such as the design of wheels of high speed trains and the aeroplane engine. Experimentally it has been found that this type of

fatigue is closely related to a ladder shape pattern of dislocations known as a persistent slip band (PSB) at a microscopic level. In this talk, a quantitative description for the formation of PSBs is proposed from two angles: 1. the motion of a single dislocation analysed by using asymptotic expansions and numerical simulations; 2. the collective behaviour of a large number of dislocations analysed by using a method of multiple scales.

#### GCOE Seminars

14:30-15:30 Room #370 (Graduate School of Math. Sci. Bldg.)

Wave Transport in Random Media and Inverse Problems (ENGLISH)

**Manabu Machida**(University of Michigan)Wave Transport in Random Media and Inverse Problems (ENGLISH)

[ Abstract ]

Wave transport in random media is described by the radiative transport equation, which is a linear Boltzmann equation. Such transport phenomena are characterized by two optical parameters in the equation: the absorption and scattering coefficients. In this talk, inverse problems of determining optical parameters will be considered and the Lipschitz stability will be proved using a Carleman estimate. One application of this inverse problem is optical tomography, which detects tumors in a human body using (unlike X-ray CT scan) near-infrared light. I will also present tomographic images of lemon and lotus root slices which are obtained by numerically solving the radiative transport equation with the method of rotated reference frames.

Wave transport in random media is described by the radiative transport equation, which is a linear Boltzmann equation. Such transport phenomena are characterized by two optical parameters in the equation: the absorption and scattering coefficients. In this talk, inverse problems of determining optical parameters will be considered and the Lipschitz stability will be proved using a Carleman estimate. One application of this inverse problem is optical tomography, which detects tumors in a human body using (unlike X-ray CT scan) near-infrared light. I will also present tomographic images of lemon and lotus root slices which are obtained by numerically solving the radiative transport equation with the method of rotated reference frames.

### 2011/12/26

#### Algebraic Geometry Seminar

15:30-17:00 Room #122 (Graduate School of Math. Sci. Bldg.)

Birational unboundedness of Q-Fano varieties and rationally connected strict Mori fiber spaces (JAPANESE)

**Takuzo Okada**(Kyoto University)Birational unboundedness of Q-Fano varieties and rationally connected strict Mori fiber spaces (JAPANESE)

[ Abstract ]

It has been known that suitably restricted classes of Q-Fano varieties are bounded. I will talk about the birational unboundedness of (log terminal) Q-Fano varieties with Picard number one and of rationally connected strict Mori fiber spaces in each dimension $¥geq 3$. I will explain the idea of the proof which will be done after passing to a positive characteristic.

It has been known that suitably restricted classes of Q-Fano varieties are bounded. I will talk about the birational unboundedness of (log terminal) Q-Fano varieties with Picard number one and of rationally connected strict Mori fiber spaces in each dimension $¥geq 3$. I will explain the idea of the proof which will be done after passing to a positive characteristic.

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