## Seminar information archive

### 2018/07/02

#### Tokyo Probability Seminar

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
Toru SERA (Graduate School of Science, Kyoto University)
Distributional limit theorems for intermittent maps (JAPANESE)

#### Seminar on Geometric Complex Analysis

10:30-12:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Katsuhiko Matsuzaki (Waseda University)
Rigidity of certain groups of circle homeomorphisms and Teichmueller spaces (JAPANESE)
[ Abstract ]
In this talk, I explain a complex analytic method and its applications
for the study of quasisymmetric homeomorphisms of the circle by extending them to the unit disk quasiconformally.
In RIMS conference "Open Problems in Complex Geometry'' held in 2010,
I gave a talk entitled "Problems on infinite dimensional Teichmueller spaces", and
mentioned several problems on the fixed points of group actions on
the universal Teichmueller space and its subspaces, and the rigidity of conjugation of
certain groups of circle homeomorphisms.
I will report on the development of these problems since then.

#### PDE Real Analysis Seminar

10:30-11:30   Room #056 (Graduate School of Math. Sci. Bldg.)
László Székelyhidi Jr. (Universität Leipzig)
Convex integration in fluid dynamics (English)
[ Abstract ]
In the talk we present the technique of convex integration for constructing weak solutions to various equations in fluid mechanics.
We will focus on the recent resolution of Onsagers conjecture, but also discuss further directions and in particular the applicability to dissipative systems.

### 2018/06/29

#### Colloquium

15:30-16:30   Room #056 (Graduate School of Math. Sci. Bldg.)
Kazuhiro Ishige (The University of Tokyo)
Power concavity for parabolic equations (日本語)

### 2018/06/27

#### Operator Algebra Seminars

16:45-18:15   Room #126 (Graduate School of Math. Sci. Bldg.)
Seung-Hyeok Kye (Seoul National Univ.)
TBA

### 2018/06/26

#### Algebraic Geometry Seminar

15:30-17:00   Room #122 (Graduate School of Math. Sci. Bldg.)
Kiwamu Watanabe (Saitama)
Varieties with nef diagonal (English)
[ Abstract ]
For a smooth projective variety $X$, we consider when the diagonal $Δ _X$ is nef as a
cycle on $X \times X$. In particular, we give a classication of complete intersections and smooth
del Pezzo varieties where the diagonal is nef. We also study the nefness of the diagonal for
spherical varieties. This is a joint work with Taku Suzuki.

#### Tuesday Seminar of Analysis

16:50-18:20   Room #128 (Graduate School of Math. Sci. Bldg.)
OGAWA Takayoshi (Tohoku University)
The Cauchy problem of the drift-diffusion system in R^n (日本語)
[ Abstract ]
We consider the Cauchy problem of the drift-diffusion system in the whole space. Introducing the scaling critical case, we consider the solvability of the drift-diffusion system in the whole space and give some large time behavior of solutions. This talk is based on a collaboration with Masaki Kurokiba and Hiroshi Wakui.

### 2018/06/25

#### Tokyo Probability Seminar

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
Yushi HAMAGUCHI (Graduate School of Science, Kyoto University)
BSDEs driven by cylindrical martingales with application to approximate hedging in bond markets (JAPANESE)

#### Discrete mathematical modelling seminar

17:30-18:30   Room #056 (Graduate School of Math. Sci. Bldg.)
Anton Dzhamay (University of Northern Colorado)
Gap Probabilities and discrete Painlevé equations
[ Abstract ]
It is well-known that important statistical quantities, such as gap probabilities, in various discrete probabilistic models of random matrix type satisfy the so-called discrete Painlevé equations, which provides an effective way to computing them. In this talk we discuss this correspondence for a particular class of models, known as boxed plane partitions (equivalently, lozenge tilings of a hexagon). For uniform probability distribution, this is one of the most studied models of random surfaces. Borodin, Gorin, and Rains showed that it is possible to assign a very general elliptic weight to the distribution, with various degenerations of this weight corresponding to the degeneration cascade of discrete polynomial ensembles, such as Racah and Hahn ensembles and their q-analogues. This also correspond to the degeneration scheme of discrete Painlevé equations, due to Sakai. In this talk we consider the q-Hahn and q-Racah ensembles and corresponding discrete Painlevé equations of types q-P(A_{2}^{(1)}) and q-P(A_{1}^{(1)}).
This is joint work with Alisa Knizel (Columbia University)

#### Seminar on Geometric Complex Analysis

10:30-12:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Stephen McKeown (Princeton University)
Cornered Asymptotically Hyperbolic Spaces
[ Abstract ]
This talk will concern cornered asymptotically hyperbolic spaces, which have a finite boundary in addition to the usual infinite boundary. I will first describe the construction a normal form near the corner for these spaces. Then I will discuss formal existence and uniqueness, near the corner, of asymptotically hyperbolic Einstein metrics, with a CMC-umbilic condition imposed on the finite boundary. This is analogous to the Fefferman-Graham construction for the ordinary, non-cornered setting. Finally, I will present work in progress regarding scattering on such spaces.

### 2018/06/22

#### Lectures

16:00-17:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Michael Harrison (Lehigh University)
Fibrations of R^3 by oriented lines
[ Abstract ]
Is it possible to cover 3-dimensional space by a collection of lines, such that no two lines intersect and no two lines are parallel? More precisely, does there exist a fibration of R^3 by pairwise skew lines? We give some examples and provide a complete topological classification of such objects, by exhibiting a deformation retract from the space of skew fibrations of R^3 to its subspace of Hopf fibrations. As a corollary of the proof we obtain Gluck and Warner's classification of great circle fibrations of S^3. We continue with some recent results regarding contact structures on R^3 which are naturally induced by skew fibrations. Finally, we discuss fibrations of R^3 which may contain parallel fibers, and discuss when such objects induce contact structures.

### 2018/06/20

#### Number Theory Seminar

17:00-18:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Ippei Nagamachi (University of Tokyo)
Criteria for good reduction of hyperbolic polycurves (JAPANESE)
[ Abstract ]
We give good reduction criteria for hyperbolic polycurves, i.e., successive extensions of families of curves, under mild assumption. These criteria are higher dimensional versions of the good reduction criterion for hyperbolic curves given by Oda and Tamagawa. In this talk, we construct homotopy exact sequences by using intermediate quotient groups of geometric etale fundamental groups of hyperbolic polycurves.

### 2018/06/19

#### Algebraic Geometry Seminar

15:30-17:00   Room #122 (Graduate School of Math. Sci. Bldg.)
Yasuhiro Wakabayashi (TIT)
Dormant Miura opers and Tango structures (Japanese (writing in English))
[ Abstract ]
Only Japanese abstract is available.

#### Tuesday Seminar of Analysis

16:50-18:20   Room #128 (Graduate School of Math. Sci. Bldg.)
Rowan Killip (UCLA)
KdV is wellposed in $H^{-1}$ (English)

#### Numerical Analysis Seminar

16:50-18:20   Room #002 (Graduate School of Math. Sci. Bldg.)
Shuji Yoshikawa (Oita University)
Small data global existence for the semi-discrete scheme of a model system of hyperbolic balance laws (Japanese)

#### Tuesday Seminar on Topology

17:00-18:30   Room #056 (Graduate School of Math. Sci. Bldg.)
Hokuto Konno (The University of Tokyo)
Characteristic classes via 4-dimensional gauge theory (JAPANESE)
[ Abstract ]
Using gauge theory, more precisely SO(3)-Yang-Mills theory and Seiberg-Witten theory, I will construct characteristic classes of 4-manifold bundles. These characteristic classes are extensions of the SO(3)-Donaldson invariant and the Seiberg-Witten invariant to families of 4-manifolds, and can detect non-triviality of smooth 4-manifold bundles. The basic idea of the construction of these characteristic classes is to consider an infinite dimensional analogue of classical characteristic classes of manifold bundles, typified by the Mumford-Morita-Miller classes for surface bundles.

#### Tuesday Seminar on Topology

14:30-16:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Kenji Fukaya (Simons center, SUNY)
Relative and equivariant Lagrangian Floer homology and Atiyah-Floer conjecture (JAPANESE)
[ Abstract ]
Atiyah-Floer conjecture concerns a relationship between Floer homology in Gauge theory and Lagrangian Floer homology. One of its difficulty is that the symplectic manifold on wich we consider Lagrangian Floer homology is in general singular. In this talk I will explain that, by using relative and equivariant version of Lagrangian Floer homology, we can resolve this problem and can at least state the conjecture as rigorous mathematical conjecture.

### 2018/06/18

#### Tokyo Probability Seminar

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
Hideki TANEMURA (Department of Mathematics, Keio University)
(JAPANESE)

#### Operator Algebra Seminars

16:45-18:15   Room #122 (Graduate School of Math. Sci. Bldg.)
Ryszard Nest (Copenhagen Univ.)
Equivariant index theorem (English)

### 2018/06/13

#### Operator Algebra Seminars

16:45-18:15   Room #126 (Graduate School of Math. Sci. Bldg.)
Ryokichi Tanaka (Tohoku Univ.)
Poisson boundary for the discrete affine group (English)

### 2018/06/12

#### Algebraic Geometry Seminar

15:30-17:00   Room #122 (Graduate School of Math. Sci. Bldg.)
Takahiro Shibata (Kyoto)
Ample canonical heights for endomorphisms on projective varieties (English or Japanese)
[ Abstract ]
Given a smooth projective variety on a number field and an
endomorphism on it, we would like to know how the height of a point
grows by iteration of the action of the endomorphism. When the
endomorphism is polarized, Call and Silverman construct the canonical
height, which is an important tool for the calculation of growth of
heights. In this talk, we will give a generalization of the Call-
Silverman canonical heights for not necessarily polarized endomorphisms,
ample canonical heights, and propose an analogue of the Northcott
finiteness theorem as a conjecture. We will see that the conjecture
holds when the variety is an abelian variety or a surface.

#### Tuesday Seminar on Topology

17:00-18:30   Room #056 (Graduate School of Math. Sci. Bldg.)
Yoshihiko Mitsumatsu (Chuo University)
Turbulization of 2-dimensional foliations on 4-manifolds (JAPANESE)
[ Abstract ]
This is a report on a joint work with Elmar VOGT(Freie Universität Berlin). For codimension 1 foliations, the process of turbulization, i.e., inserting a Reeb component along a closed transversal, is well-known, while for higher codimensional foliation, similar processes were not understood until around 2006.

In this talk, first we formulate the turbulization along a closed transversal. Then in our dimension setting, namely 2-dimensional foliations on 4-manifolds ((4,2)-foliations), a cohomological criterion is given for a given transversal to a foliation, which tells the turbulization is possible or not, relying on the Thurston's h-principle. Also we give cocrete geometric constructions of turbulizations.

The cohomological criterion for turbulization is deduced from a more general criterion for a given embedded surface to be a compact leaf or a closed transversal of some foliation, which is stated in terms of the euler classes of tangent and normal bndle of the foliation to look for. The anormalous cohomological solutions for certain cases suggested the geometric realization of turbulization, while the cohomological criterion is obtained by the h-principle.

Some other modifications are also formulated for (4,2)-foliations and their possibility are assured by the anormalous solutions mentioned above. For some of them, good geometric realizations are not yet known. So far the difficulty lies on the problem of the connected components of the space of representations of the surface groups to Diff S^1.

If the time permits, some special features on the h-principle for 2-dimensional foliations are also explained.

#### Lectures

15:00-16:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Alexander Kupers (Harvard University)
Cellular E_2-algebras and the unstable homology of mapping class groups

[ Abstract ]
We discuss joint work with Soren Galatius and Oscar Randal-Williams on the application of higher-algebraic techniques to classical questions about the homology of mapping class groups. This uses a new "multiplicative" approach to homological stability -- in contrast to the "additive" one due to Quillen -- which has the advantage of providing information outside of the stable range.

### 2018/06/11

#### Seminar on Geometric Complex Analysis

10:30-12:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Yusaku Tiba (Ochanomizu University)
Cohomology of non-pluriharmonic loci (JAPANESE)
[ Abstract ]
In this talk, we study a pseudoconvex counterpart of the Lefschetz hyperplane theorem.
We show a relation between the cohomology of a pseudoconvex domain and the cohomology of the non-pluriharmonic locus of an exhaustive plurisubharmonic function.

### 2018/06/06

#### Number Theory Seminar

17:30-18:30   Room #056 (Graduate School of Math. Sci. Bldg.)
Nicolas Templier (Cornell University)
On the Ramanujan conjecture for automorphic forms over function fields
[ Abstract ]
Let G be a reductive group over a function field of large enough characteristic. We prove the temperedness at unramified places of automorphic representations of G, subject to a local assumption at one place, stronger than supercuspidality. Such an assumption is necessary, as was first shown by Saito-Kurokawa and Howe-Piatetskii-Shapiro in the 70's. Our method relies on the l-adic geometry of Bun_G, and on trace formulas. Work with Will Sawin.