## 過去の記録

### 2018年05月07日(月)

#### 複素解析幾何セミナー

10:30-12:00   数理科学研究科棟(駒場) 128号室

Proper holomorphic mappings and generalized pseudoellipsoids (JAPANESE)
[ 講演概要 ]
We study the classification of proper holomorphic mappings between generalized pseudoellipsoids of different dimensions.

Huang proved some classification theorems of proper holomorphic mappings between balls of different dimensions, which are called gap theorems. Our present theorems are their weakly pseudoconvex versions.

In the theorem, classified mapping is so-called a variables splitting mapping and each component is derived from a homogeneous proper polynomial mapping between balls.

The essential methods are the ''good'' decompositions of CR vector bundle and reduction the mapping under consideration to the mapping of balls. By this reduction, we can apply Huang's gap theorem.

#### 東京確率論セミナー

16:00-17:30   数理科学研究科棟(駒場) 126号室

(JAPANESE)
[ 講演概要 ]

[1] Eiki Iyoda, Kazuya Kaneko, and Takahiro Sagawa, Phys. Rev. Lett. 119, 100601 (2017).
[2] Toru Yoshizawa, Eiki Iyoda, Takahiro Sagawa, arXiv:1712.07289, accepted by Phys. Rev. Lett. (2018).
[ 講演参考URL ]
http://www.taksagawa.com

#### FMSPレクチャーズ

15:00-17:00   数理科学研究科棟(駒場) 123号室

Sug Woo Shin 氏 (University of California, Berkeley)
Introduction to the Langlands-Rapoport conjecture (ENGLISH)
[ 講演概要 ]
In 1970s Langlands envisioned a program to compute the Hasse-Weil zeta functions of Shimura varieties as an alternating product of automorphic L-functions, which in particular implies the meromorphic continuation and functional equation for the zeta functions. In 1987, Langlands and Rapoport formulated a precise and far-reaching conjecture describing the set of points of Shimura varieties modulo p as an essential step towards the goal. The program has been largely carried out by Langlands, Kottwitz, and others for PEL-type Shimura varieties with striking applications to the local and global Langlands correspondences (which in turn led to further applications). We have started to understand the more general Hodge-type and abelian-type cases only recently, thanks to Kisin's work on the Langlands-Rapoport conjecture in the good reduction case. The lecture aims to give a gentle introduction to his seminal paper. After a brief introduction, the lecture is divided into four parts.
(i) Shimura varieties: We introduce Shimura varieties of Hodge type and abelian type and their integral models.
(ii) Statement of the conjecture: After setting up the language of
Galois gerbs, we state the Langlands-Rapoport conjecture.
(iii) Sketch of Kisin's proof: We sketch Kisin's proof of the conjecture for Shimura varieties of Hodge type.
(iv) Counting fixed points: Following forthcoming work of Kisin, Y. Zhu, and the speaker, we explain how to apply the Langlands-Rapoport conjecture to count fixed-points of
Hecke-Frobenius correspondences.
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_SugWooShin.pdf

### 2018年05月02日(水)

#### 作用素環セミナー

16:45-18:15   数理科学研究科棟(駒場) 126号室
Gabor Szabo 氏 (Copenhagen Univ.)
Classification of Rokhlin flows (English)

### 2018年04月24日(火)

#### 代数幾何学セミナー

15:30-17:00   数理科学研究科棟(駒場) 122号室

BIRATIONAL BOUNDEDNESS OF RATIONALLY CONNECTED CALABI–YAU 3-FOLDS
(English)
[ 講演概要 ]
Firstly, we show that rationally connected Calabi–Yau 3- folds with kawamata log terminal (klt) singularities form a birationally bounded family, or more generally, rationally connected 3-folds of ε-CY type form a birationally bounded family for ε > 0. Then we focus on ε-lc log Calabi–Yau pairs (X, B) such that coefficients of B are bounded from below away from zero. We show that such pairs are log bounded modulo flops. As a consequence, we show that rationally connected klt Calabi–Yau 3-folds with mld bounding away from 1 are bounded modulo flops.

#### トポロジー火曜セミナー

17:00-18:30   数理科学研究科棟(駒場) 056号室
Tea: Common Room 16:30-17:00

Singular Fibers of smooth maps and Cobordism groups (JAPANESE)
[ 講演概要 ]
Following the pioneering work of R.Thom, cobordism groups of smooth maps have been studied by some mathematicians. Especially, cobordism groups of Morse functions on closed manifolds was studied by O.Saeki and K.Ikegami, B.Kalmar. In this talk, we will introduce cobordism groups among Morse functions on compact manifolds with boundary and study the cobordism groups are trivial or not by using the theory of the universal complex of singular fibers of smooth maps.

### 2018年04月23日(月)

#### 複素解析幾何セミナー

10:30-12:00   数理科学研究科棟(駒場) 128号室

Degeneration and bifurcation of quadratic endomorphisms of P^2
towards a H¥'enon map (JAPANESE)
[ 講演概要 ]
The space of quadratic holomorphic endomorphisms of P^2 (over C) is
canonically identified with the complement of the zero locus of the
resultant form on P^{17}, and all H¥'enon maps, which are (the only)
interesting ones among all the quadratic polynomial automorphisms of C^2,
live in this zero locus.

We will talk about our joint work with Fabrizio Bianchi (Imperial College,
London) on the (algebraic) degeneration of quadratic endomorphisms of C^2
towards H¥'enon maps in terms of Berteloot-Bianchi-Dupont's
bifurcation/unstability theory of holomorphic families of endomorphisms of P^k,
which mostly generalizes Ma¥~n¥'e-Sad-Sullivan, Lyubich, and DeMarco's seminal
and similar theory on P^1.

Some preliminary knowledge on ergodic theory and pluripotential theory
would be desirable, but not be assumed.

#### 東京確率論セミナー

16:00-17:30   数理科学研究科棟(駒場) 126号室

Functional central limit theorems for non-symmetric random walks on nilpotent covering graphs (JAPANESE)
[ 講演概要 ]
ベキ零群を被覆変換群とするような有限グラフの被覆グラフのことをベキ零被覆グラフと呼ぶ。結晶格子(被覆変換群がアーベル群の場合)上のランダムウォークに関してはすでに多くの極限定理が, 離散幾何解析の枠組みで得られている。我々は以前にこれらの研究の延長としてベキ零被覆グラフ上の非対称ランダムウォークの汎関数中心極限定理を考察し,スケール極限として捉えたベキ零Lie群値拡散過程に, ランダムウォークの非対称性からくるドリフト項が現れることをいくつかの技術的な仮定の下で示した。この結果は難波氏が, 2016年7月の本セミナーで報告したが,その後, このドリフト項が実現写像のambiguityによらずに定まる事が分かっただけでなく, 従来の技術的な仮定の多くをはずすことにも成功した。時間があればラフパス理論との関連および証明の概略についても話したい。

### 2018年04月18日(水)

#### 作用素環セミナー

16:45-18:15   数理科学研究科棟(駒場) 126号室

#### 代数学コロキウム

16:00-17:00   数理科学研究科棟(駒場) 002号室
Ildar Gaisin 氏 (東京大学数理科学研究科)
Fargues' conjecture in the GL_2-case (ENGLISH)
[ 講演概要 ]
Recently Fargues announced a conjecture which attempts to geometrize the (classical) local Langlands correspondence. Just as in the geometric Langlands story, there is a stack of G-bundles and a Hecke stack which one can define. The conjecture is based on some conjectural objects, however for a cuspidal Langlands parameter and a minuscule cocharacter, we can define every object in the conjecture, assuming only the local Langlands correspondence. We study the geometry of the non-semi-stable locus in the Hecke stack and as an application we will show the Hecke eigensheaf property of Fargues conjecture holds in the GL_2-case and a cuspidal Langlands parameter. This is joint work with Naoki Imai.

#### 代数学コロキウム

17:10-18:10   数理科学研究科棟(駒場) 002号室

p進代数群の法p表現とHecke環 (JAPANESE)
[ 講演概要 ]
p進代数群の，標数pの体上における表現（法p表現）について，付随するHecke環の表現論の関わりとともにお話をします．これは，G. Henniart，F. HerzigおよびM.-F. Vignérasとの共同研究に基づきます．

### 2018年04月17日(火)

#### PDE実解析研究会

10:30-11:30   数理科学研究科棟(駒場) 056号室

Global existence of a strong solution to the Navier-Stokes equations in a curved thin domain (Japanese)
[ 講演概要 ]
In this talk, we consider the Navier-Stokes equations with Navier's slip boundary conditions in a three-dimensional curved thin domain around a closed surface.
We establish the global-in-time existence of a strong solution for large data when the width of the thin domain is very small.
A key idea is to decompose a three-dimensional vector field into the average part which is almost two-dimensional and the residual part to which we can apply Poincaré type inequalities.
Such decomposition enables us to derive a good estimate for the inner product of the inertia term and the viscous term, which is essential for our arguments.

#### 代数幾何学セミナー

15:30-17:00   数理科学研究科棟(駒場) 122号室

SNC log symplectic structures on Fano products (English/Japanese)
[ 講演概要 ]
In 2014, Lima and Pereira gave a characterization of the even-dimensional projective space in terms of log symplectic Poisson structures. After that Pym gave an another more algebraic proof. In this talk, we will extend the result of Lima and Pereira to the case that the variety is a product of Fano varieties with the cyclic Picard group. This will be proved by extending Pym's proof. As a corollary, we will obtain a characterization of the projective space of all dimensions.

#### 数値解析セミナー

16:50-18:20   数理科学研究科棟(駒場) 002号室

[ 講演概要 ]

#### トポロジー火曜セミナー

17:00-18:30   数理科学研究科棟(駒場) 056号室
Tea: Common Room 16:30-17:00
Tamás Kálmán 氏 (東京工業大学)
Tight contact structures on Seifert surface complements and knot invariants (ENGLISH)
[ 講演概要 ]
In joint work with Daniel Mathews, we examined complements of standard Seifert surfaces of special alternating links and used Honda's method to enumerate those tight contact structures on them whose dividing sets are isotopic to the link. The number turns out to be the leading coefficient of the Alexander polynomial. The proof is rather combinatorial in nature; for example, the Euler classes of the contact structures are identified with `hypertrees' in a certain hypergraph. Using earlier results with Hitoshi Murakami and Alexander Postnikov, this yields a connection between contact topology and the Homfly polynomial. We also found that the contact invariants of our structures form a basis for the sutured Floer homology of the manifold.

### 2018年04月16日(月)

#### 複素解析幾何セミナー

10:30-12:00   数理科学研究科棟(駒場) 128号室

ラプラシアンの第１固有値を最大化する閉曲面上の計量について (JAPANESE)
[ 講演概要 ]

### 2018年04月11日(水)

#### 代数学コロキウム

17:30-18:30   数理科学研究科棟(駒場) 056号室
Minhyong Kim 氏 (University of Oxford)
Non-abelian cohomology and Diophantine geometry (ENGLISH)
[ 講演概要 ]
This lecture will review the construction of moduli schemes of torsors for sheaves of pro-unipotent groups and their applications to the resolution of Diophantine problems.

（本講演は「東京北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, Morningside Center of Mathematics と IHES の双方向同時中継で行います．今回はパリからの中継です．）

### 2018年04月10日(火)

#### トポロジー火曜セミナー

17:00-18:30   数理科学研究科棟(駒場) 056号室
Tea: Common Room 16:30-17:00

２次元結び目のモース・ノビコフ数について (JAPANESE)
[ 講演概要 ]
2001年にPajitnov, Rudolph, Weberは，古典的絡み目に対してMorse-Novikov数を定義し，その基本的な性質を研究した．この不変量は，Alexander多項式やNovikovホモロジーおよびそれらの「ねじれ版」との関連から盛んに研究されている．本講演では，２次元結び目に対してMorse-Novikov数を定義し，いくつかの性質を述べる．特に，２次元結び目のモーション・ピクチャーやスピン構成法との関係について解説する．尚，本講演の内容はAndrei Pajitnov氏（ナント大学）との共同研究にもとづいている．

### 2018年04月09日(月)

#### 代数幾何学セミナー

15:30-17:00   数理科学研究科棟(駒場) 122号室

Luca Rizzi 氏 (Udine)
Adjoint forms on algebraic varieties (English)
[ 講演概要 ]
The so called adjoint theory was introduced by A. Collino and G.P. Pirola in the case of smooth algebraic curves and then generalized by G.P. Pirola and F. Zucconi in the case of smooth algebraic varieties of arbitrary dimension.
The main idea of this theory is to study particular differential forms, called adjoint forms, on an algebraic variety to obtain information on the infinitesimal deformations of the variety itself.
The natural context for the application of this theory is given by Torelli-type problems, in particular infinitesimal Torelli problems.

#### 代数幾何学セミナー

13:30-15:00   数理科学研究科棟(駒場) 122号室

David Hyeon 氏 (ソウル大学校)
Commuting nilpotents, punctual Hilbert schemes and jet bundles (ENGLISH)
[ 講演概要 ]
Pairs of commuting nilpotent matrices have been extensively studied, especially from the view point of quivers, but the space of commuting nilpotents modulo simultaneous conjugation has not received any attention at all despite its moduli theory flavor. I will explain how a 'moduli space' can be constructed via two different methods and demonstrate many interesting properties of the space:

- It is isomorphic to an open subscheme of a punctual Hilbert scheme.
- Over the field of complex numbers, it is diffeomorphic to a direct sum of twisted tangent bundles over a projective space.
- It is isomorphic to a bundle of regular jets.
- It gives examples of affine space bundles that are not vector bundles.

This is a joint work with W. Haboush (Illinois) and G. Bérczi (Zurich).

### 2018年04月06日(金)

#### 談話会・数理科学講演会

15:30-16:30   数理科学研究科棟(駒場) 123号室

[ 講演概要 ]

ぐことはよく知られているが、精子や鞭毛虫などの微小生物の中にも同様に流れ
に逆らって泳ぐものがいる。本講演では、微小スケールの流体力学の導入から始
め、流体方程式を解析することで生き物の泳ぎを理解する試みについてお話しす
る。後半では自身の微生物走流性の２次元流体モデルの研究を紹介し、複雑な現

### 2018年04月03日(火)

#### トポロジー火曜セミナー

17:00-18:30   数理科学研究科棟(駒場) 056号室
Tea: Common Room 16:30-17:00

Chain level loop bracket and pseudo-holomorphic disks (JAPANESE)
[ 講演概要 ]
Let $L$ be a Lagrangian submanifold in a symplectic vector space which is closed, oriented and spin. Using virtual fundamental chains of moduli spaces of nonconstant pseudo-holomorphic disks with boundaries on $L$, one can define a Maurer-Cartan element of a Lie bracket operation in string topology (the loop bracket) defined at chain level. This idea is due to Fukaya, who also pointed out its important consequences in symplectic topology. In this talk I will explain how to rigorously carry out this idea. Our argument is based on a string topology chain model previously introduced by the speaker, and theory of Kuranishi structures on moduli spaces of pseudo-holomorphic disks, which has been developed by Fukaya-Oh-Ohta-Ono.

#### 東京無限可積分系セミナー

15:00-16:00   数理科学研究科棟(駒場) 002号室

Screening Operators and Parabolic inductions for W-algebras
(ENGLISH)
[ 講演概要 ]
（アファイン）W代数とはDrinfeld-Sokorov reductionによって定義される頂点代数
の族である。本講演ではアファインLie代数の脇本表現から誘導される、一般のW代数
の自由場表示を考える。その時、W代数の脇本表現とも呼べる表現が構成され、自由

sevによって構成された有限W代数におけるParabolic inductionのW代数版が得られる
ことを示す。特にA型の場合ではBrundan-Klshchevのcoproductのchiralizationにな
り、BCD型の特殊な場合ではその類似が発見できる。

### 2018年03月30日(金)

#### トポロジー火曜セミナー

15:00-16:30   数理科学研究科棟(駒場) 056号室
Tea: Common Room 16:30-17:00
Matteo Felder 氏 (University of Geneva)
Graph Complexes and the Kashiwara-Vergne Lie algebra (ENGLISH)
[ 講演概要 ]
The Kashiwara-Vergne Lie algebra krv was introduced by A. Alekseev and C. Torossian. It describes the symmetries of the Kashiwara-Vergne problem in Lie theory. It has been shown to contain the Grothendieck-Teichmüller Lie algebra grt as a Lie subalgebra. Conjecturally, these two Lie algebras are expected to be isomorphic. An important theorem by T. Willwacher states that in degree zero the cohomology of M. Kontsevich's graph complex GC is isomorphic to grt. We will show how T. Willwacher's result induces a natural way to define a nested sequence of Lie subalgebras of krv whose intersection is grt. This infinite family therefore interpolates between the two Lie algebras. For this we will recall several techniques from the theory of graph complexes. If time permits, we will then sketch how one might generalize these notions to establish a "genus one" analogue of T. Willwacher theorem. More precisely, we will define a chain complex whose degree zero cohomology is given by a Lie subalgebra of the elliptic Grothendieck-Teichmüller Lie algebra introduced by B. Enriquez. The last part is joint work in progress with T. Willwacher.

#### トポロジー火曜セミナー

17:00-18:30   数理科学研究科棟(駒場) 056号室
Tea: Common Room 16:30-17:00
Florian Naef 氏 (Massachusetts Institute of Technology)
Goldman-Turaev formality in genus 0 from the KZ connection (ENGLISH)
[ 講演概要 ]
Using the intersection and self-intersection of loops on a surface one can define the Goldman-Turaev Lie bialgebra. By earlier joint work with A. Alekseev, N. Kawazumi and Y. Kuno it is known that the linearization problem of the Goldman-Turaev Lie bialgebra is closely related to the Kashiwara-Vergne problem and hence to Drinfeld associators. It turns out that in the case of a genus 0 surface and over the field of complex numbers there is a very direct and explicit proof of the formality of the Goldman-Turaev Lie bialgebra using the monodromy of the Knizhnik-Zamolodchikov connection. This is joint work with Anton Alekseev.