Seminar information archive

Seminar information archive ~07/21Today's seminar 07/22 | Future seminars 07/23~

thesis presentations

11:00-12:15   Online
Masatoshi Goda (Graduate School of Mathematical Sciences University of Tokyo)
Statistical inference for Hawkes processes
[ Reference URL ]
https://forms.gle/bdsntP4pZ4TMaehF9

thesis presentations

14:45-16:00   Online
Yusuke Sato (Graduate School of Mathematical Sciences University of Tokyo)
Multidimensional continued fractions and Fujiki-Oka resolutions of cyclic quotient singularities
[ Reference URL ]
https://forms.gle/bdsntP4pZ4TMaehF9

thesis presentations

11:00-12:15   Online
Taketo Sano (Graduate School of Mathematical Sciences University of Tokyo)
On functoriality and spatial refinements of Khovanov homology and its variants
[ Reference URL ]
https://forms.gle/bdsntP4pZ4TMaehF9

thesis presentations

14:45-16:00   Online
Hiroshi Takase (Graduate School of Mathematical Sciences University of Tokyo)
Inverse problems for hyperbolic partial differential equations with time-dependent coefficients
[ Reference URL ]
https://forms.gle/bdsntP4pZ4TMaehF9

thesis presentations

14:45-16:00   Online
Mayuko Yamashita (RIMS, Kyoto University)
Differential models for the Anderson dual to bordism theories and invertible QFT’s
[ Reference URL ]
https://forms.gle/bdsntP4pZ4TMaehF9

2022/01/25

Tuesday Seminar on Topology

17:00-18:00   Online
Pre-registration required. See our seminar webpage.
Xiaobing Sheng (The Univesity of Tokyo)
Some obstructions on subgroups of the Brin-Thompson group $2V$ (ENGLISH)
[ Abstract ]
Motivated by Burillo, Cleary and Röver's summary of the obstruction for subgroups of Thompson's group $V$, we investigate the higher dimensional version, the group $2V$ and found out that they have similar obstructions on torsion subgroups and certain Baumslag-Solitar groups.
[ Reference URL ]
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html

2022/01/24

Seminar on Geometric Complex Analysis

10:30-12:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Junjiro Noguchi (The University of Tokyo)
Analytic Ax-Schanuel Theorem for semi-abelian varieties and Nevanlinna theory (Japanese)
[ Abstract ]
The present study is motivated by $\textit{Schanuel Conjecture}$, which in particular implies the algebraic independence of $e$ and $\pi$. Our aim is to explore, as a transcendental functional analogue of Schanuel Conjecture, the value distribution theory (Nevanlinna theory) of the entire curve $\widehat{\mathrm{ex}}_A f:=(\exp_Af,f):\mathbf{C} \to A \times \mathrm{Lie}(A)$ associated with an entire curve $f: \mathbf{C} \to \mathrm{Lie}(A)$, where $\exp_A:\mathrm{Lie}(A)\to A$ is an exponential map of a semi-abelian variety $A$.

We firstly give a Nevanlinna theoretic proof to the $\textit{analytic Ax-Schanuel Theorem}$ for semi-abelian varieties, which was proved by J. Ax 1972 in the case of formal power series $\mathbf{C}[[t]]$ (Ax-Schanuel Theorem). We assume some non-degeneracy condition for $f$ such that in the case of $A=(\mathbf{C}^*)^n$ and $\mathrm{Lie}((\mathbf{C}^*)^n)=\mathbf{C}^n$, the elements of the vector-valued function $f(z)-f(0)$ are $\mathbf{Q}$-linearly independent. Then by the method of Nevanlinna theory (the Log Bloch-Ochiai Theorem), we prove that $\mathrm{tr.deg}_\mathbf{C}\, \widehat{\mathrm{ex}}_A f \geq n+ 1.$

Secondly, we prove a $\textit{Second Main Theorem}$ for $\widehat{\mathrm{ex}}_A f$ and an algebraic divisor $D$ on $A \times \mathrm{Lie}(A)$ with compactifications $\bar D \subset \bar A \times \overline{\mathrm{Lie}(A)}$ such that
\[
T_{\widehat{\mathrm{ex}}_Af}(r, L({\bar D})) \leq N_1 (r,
(\widehat{\mathrm{ex}}_A f)^* D)+
\varepsilon T_{\exp_Af}(r)+O(\log r) ~~ ||_\varepsilon.
\]
We will also deal with the intersections of $\widehat{\mathrm{ex}}_Af$ with higher codimensional algebraic cycles of $A \times \mathrm{Lie}(A)$ as well as the case of higher jets.
[ Reference URL ]
https://u-tokyo-ac-jp.zoom.us/meeting/register/tJ0vcu2rrDIqG9Rv5AT0Mpi37urIkJ1IRldB

2022/01/21

Colloquium

15:30-16:30   Online
Registration is closed (12:00, January 21).
Yoshiko Ogata (Graduate School of Mathematical Sciences, The University of Tokyo)
Classification of gapped ground state phases in quantum spin systems (JAPANESE)

Tokyo-Nagoya Algebra Seminar

16:45-18:15   Online
Please see the URL below for details on the online seminar.
Haruhisa Enomoto (Osaka Prefecture University)
Exact-categorical properties of subcategories of abelian categories 2 (Japanese)
[ Abstract ]
Quillen's exact category is a powerful framework for studying extension-closed subcategories of abelian categories, and provides many interesting questions on such subcategories.
In the first talk, I will explain the basics of some properties and invariants of exact categories (e.g. the Jordan-Holder property, simple objects, and Grothendieck monoid).
In the second talk, I will give some results and questions about particular classes of exact categories arising in the representation theory of algebras (e.g. torsion(-free) classes over path algebras and preprojective algebras).
If time permits, I will discuss questions of whether these results can be generalized to extriangulated categories (extension-closed subcategories of triangulated categories).
[ Reference URL ]
http://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html

2022/01/20

Seminar on Probability and Statistics

15:00-16:10   Room # (Graduate School of Math. Sci. Bldg.)
Yoshimasa Uematsu (-)
-
[ Reference URL ]
https://docs.google.com/forms/d/e/1FAIpQLSdH8oP72k7-qsHigZBBZ4F6N-bGIJ6BcOWgKLhted2ohGSBeg/viewform

2022/01/19

Mathematical Biology Seminar

15:00-16:00   Online
Tsuyoshi Kajiwara (Professor Emeritus, Okayama University)
Destabilization induced by time delay, immunity and absorbing effect
(Japanese)
[ Reference URL ]
オンラインですので,参加希望のかたは稲葉(inaba@ms.u-tokyo.ac.jp)へご連絡ください.

Seminar on Probability and Statistics

14:30-16:00   Room # (Graduate School of Math. Sci. Bldg.)
Martin Hazelton (Otago University)
Dynamic fibre samplers for linear inverse problems
[ Abstract ]
Asia-Pacific Seminar in Probability and Statistics (APSPS)
https://sites.google.com/view/apsps/home

Statistical inverse problems occur when we wish to learn about some random process that is observed only indirectly. Inference in such situations typically involves sampling possible values for the latent variables of interest conditional on the indirect observations. For count data, the latent variables are constrained to lie on a fibre (solution set for the linear system) comprising the integer lattice within a convex polytope.

Sampling the latent counts can be conducted using MCMC methods,through a random walk on this fibre. A major challenge is finding a set of basic moves that ensures connectedness of the walk over the fibre. In principle this can be done by computing a Markov basis of potential moves, but the resulting sampler can be hugely inefficient even when such a basis is computable. In this talk I will describe some current work on developing a dynamic Markov basis that generates moves on the fly. This approach can guarantee irreducibility of the sampler while gaining efficiency by increasing the probability of selecting serviceable sampling directions.
[ Reference URL ]
https://docs.google.com/forms/d/e/1FAIpQLSeoXt5v8xdQNFAKTDLoD0lttaHjV17_r7864x11mtxU1EQlhQ/viewform

2022/01/18

Operator Algebra Seminars

16:45-18:15   Online
Miho Mukohara (Univ. Tokyo)
C$^*$-simplicity of relative profinite completions of generalized Baumslag-Solitar groups

[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

Tokyo-Nagoya Algebra Seminar

15:00-16:30   Online
Please see the URL below for details on the online seminar.
Haruhisa Enomoto (Osaka Prefecture University)
Exact-categorical properties of subcategories of abelian categories 1 (Japanese)
[ Abstract ]
Quillen's exact category is a powerful framework for studying extension-closed subcategories of abelian categories, and provides many interesting questions on such subcategories.
In the first talk, I will explain the basics of some properties and invariants of exact categories (e.g. the Jordan-Holder property, simple objects, and Grothendieck monoid).
In the second talk, I will give some results and questions about particular classes of exact categories arising in the representation theory of algebras (e.g. torsion(-free) classes over path algebras and preprojective algebras).
If time permits, I will discuss questions of whether these results can be generalized to extriangulated categories (extension-closed subcategories of triangulated categories).
[ Reference URL ]
http://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html

Lie Groups and Representation Theory

17:00-18:00   Room #On line (Graduate School of Math. Sci. Bldg.)
Hideyuki Ishi (Osaka City University)
Strongly visible actions on complex domains (Japanese)
[ Abstract ]
In this century, the Cartan-Hartogs domain and its variations, on which the Bergman kernel function and the Kahler-Einstein metric can be computed explicitly, have been actively studied. Reasoning that strongly visible actions on the domains enable such nice calculations, we introduce a new type of complex domain analogous to the Cartan-Hartogs domain, and present a research plan about harmonic analysis over the domain.

2022/01/13

Information Mathematics Seminar

16:50-18:35   Online
Keita Xagawa (NTT)
Lattice-based cryptography and its applications (Japanese)
[ Abstract ]
Explanation on lattice-based cryptography and its applications
[ Reference URL ]
https://docs.google.com/forms/d/1WLEbsA2aQTXgdE2ynrumJOG-Z4AVWqcOLC-z42B4nPY

2022/01/11

Operator Algebra Seminars

16:45-18:15   Online
Akihiro Miyagawa (Kyoto University)
Rationality for operators in free semicircular elements
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

Tuesday Seminar on Topology

17:00-18:00   Online
Joint with Lie Groups and Representation Theory Seminar. See our seminar webpage.
Keiichi Maeta (The Univesity of Tokyo)
On the existence problem of Compact Clifford-Klein forms of indecomposable pseudo-Riemannian symmetric spaces with signature (n,2) (JAPANESE)
[ Abstract ]
For a homogeneous space $G/H$ and its discontinuous group $\Gamma\subset G$, the double coset space $\Gamma\backslash G/H$ is called a Clifford-Klein form of $G/H$. In the study of Clifford-Klein forms, the classification of homogeneous spaces which admit compact Clifford—Klein forms is one of the important open problems, which was introduced by Toshiyuki Kobayashi in 1980s. We consider this problem for indecomposable and reducible pseudo-Riemannian symmetric spaces with signature (n,2). We show the non-existence of compact Clifford-Klein forms for some series of symmetric spaces, and construct new compact Clifford-Klein forms of countably infinite five-dimensional pseudo-Riemannian symmetric spaces with signature (3,2).
[ Reference URL ]
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html

Lie Groups and Representation Theory

17:00-18:00   Room #on line (Graduate School of Math. Sci. Bldg.)
Joint with Tuesday Seminar on Topology.
Keiichi Maeta (The University of Tokyo)
On the existence problem of Compact Clifford-Klein forms of indecomposable pseudo-Riemannian symmetric spaces with signature (n,2) (Japanese)
[ Abstract ]
For a homogeneous space $G/H$ and its discontinuous group $\Gamma\subset G$, the double coset space $\Gamma\backslash G/H$ is called a Clifford-Klein form of $G/H$. In the study of Clifford-Klein forms, the classification of homogeneous spaces which admit compact Clifford-Klein forms is one of the important open problems, which was introduced by Toshiyuki Kobayashi in 1980s.

We consider this problem for indecomposable and reducible pseudo-Riemannian symmetric spaces with signature (n,2). We show the non-existence of compact Clifford-Klein forms for some series of symmetric spaces, and construct new compact Clifford-Klein forms of countably infinite five-dimensional pseudo-Riemannian symmetric spaces with signature (3,2).

2022/01/06

Information Mathematics Seminar

16:50-18:35   Online
Hiroshi Fujiwara (BroadBand Tower, Inc.)
Next cyber security strategy of the Japanese Government (Japanese)
[ Abstract ]
Explanation on next cyber security strategy of the Japanese government
[ Reference URL ]
https://docs.google.com/forms/d/1I3XD63V937BT_IoqRWBVN67goQAtbkSoIKs-6hfLUAM

2021/12/23

Information Mathematics Seminar

16:50-18:35   Online
Hiroshi Fujiwara (BroadBand Tower, Inc.)
The cyber attack to the Ministry of Defense-affiliated company and zero trust of Amazon/Google (Japanese)
[ Abstract ]
Explanation on the cyber attack to the Ministry of Defense-affiliated company and zero trust of Amazon/Google
[ Reference URL ]
https://docs.google.com/forms/d/1I3XD63V937BT_IoqRWBVN67goQAtbkSoIKs-6hfLUAM

2021/12/22

Number Theory Seminar

17:00-18:00   Online
Stefano Morra (Paris 8 University)
Some properties of the Hecke eigenclasses of the mod p-cohomology of Shimura curves (English)
[ Abstract ]
The mod p local Langlands program, foreseen by Serre and proposed in precise terms by C. Breuil after his p-divisible groups computations in the Breuil-Conrad-Diamond-Taylor proof of the Shimura-Taiyama-Weil conjecture, was realized in the particular case of GL_2(\mathbf{Q}_p) thanks to a vast convergence of new tools: classification of mod p-representations of GL_2(\mathbf{Q}_p), local Galois deformation techniques, local-global compatibility arguments.
When trying to extend these conjectures to more general groups, multiple problems arise (lack of classification results for smooth mod p-representations of p-adic groups, absence of explicit integral models for Galois representations with the relevant p-adic Hodge theory conditions), and the only way to formulate, and test, conjectures on a mod p local Langlands correspondence relies on its expected realization in Hecke eigenclasses of Shimura varieties (or, in other words, the expectation of a local-global compatibility of the Langlands correspondence).
In this talk we describe some properties of Hecke isotypical spaces of the mod p-cohomology of Shimura curves with infinite level at p, when the reflex field F is unramified at p and the Shimura curve arises from a quaternion algebra which is split at p. These Hecke isotypical spaces are expected to be the “good” smooth mod p-representations of GL_2(F_{\mathfrak{p}}) attached to mod p Galois representations of Gal(\overline{\mathbf{Q}_p}/F_{\mathfrak{p}}) via the expected local Langlands correspondence mod p. We will in particular comment on their Gelfand-Kirillov dimension, and their irreducibility (in particular, the finite length of these Hecke eigenspaces as GL_2(F_{\mathfrak{p}})-representations).
This is a report on a series of work joint with C. Breuil, F. Herzig, Y. Hu et B. Schraen.

2021/12/21

Tuesday Seminar on Topology

17:30-18:30   Online
Joint with Lie Groups and Representation Theory Seminar. See our seminar webpage.
Hiroki Shimakura (Tohoku University)
Classification of holomorphic vertex operator algebras of central charge 24 (JAPANESE)
[ Abstract ]
Holomorphic vertex operator algebras are imporant in vertex operator algebra theory. For example, the famous moonshine vertex operator algebra is holomorphic. One of the fundamental problems is to classify holomorphic vertex operator algebras. It is known that holomorphic vertex operator algebras of central charge 8 and 16 are lattice vertex operator algebras. I will talk about recent progress on the classification of holomorphic vertex operator algebras of central charge 24.
[ Reference URL ]
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html

Operator Algebra Seminars

16:45-18:15   Online
Wojciech Dybalski (Adam Mickiewicz University in Poznan)
Interacting massless infraparticles in 1+1 dimensions
(English)
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm

Lie Groups and Representation Theory

17:30-18:30   Room #on line (Graduate School of Math. Sci. Bldg.)
Joint with Tuesday Seminar on Topology.
Hiroki Shimakura (Tohoku University)
Classification of holomorphic vertex operator algebras of central charge 24
(Japanese)
[ Abstract ]
Holomorphic vertex operator algebras are important in vertex operator algebra theory. For example, the famous moonshine vertex operator algebra is holomorphic.
One of the fundamental problems is to classify holomorphic vertex operator algebras. It is known that holomorphic vertex operator algebras of central charge 8 and 16 are lattice vertex operator algebras.
I will talk about recent progress on the classification of holomorphic vertex operator algebras of central charge 24.

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