Seminar information archive

Seminar information archive ～04/30｜Today's seminar 05/01 | Future seminars 05/02～

2024/12/16

Seminar on Geometric Complex Analysis

10:30-12:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Laurent Stolovitch (Universite Cote d'Azur)
CR singularities and dynamical systems (English)
[ Abstract ]
In this talk, we'll survey some recent results done since the seminal work of Moser and Webster about smooth real analytic surfaces in $C^2$ which are totally real everywhere but at a point where the tangent space is a complex line. Such a point is called a singularity of the Cauchy-Riemann structure. We are interested in the holomorphic classification of these surface near the singularity. It happens that there is a deep connection with holomorphic classification of some holomorphic dynamical systems near a fixed point so that new results for the later provide new result for the former.
[ Reference URL ]
https://forms.gle/gTP8qNZwPyQyxjTj8

Tokyo Probability Seminar

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
We are having teatime from 15:15 in the common room on the second floor. Please join us.
Shu Kanazawa (Kyoto University)
Central limit theorem for linear eigenvalue statistics of the adjacency matrices of random simplicial complexes
[ Abstract ]
We consider the (higher-dimensional) adjacency matrix of the Linial-Meshulam complex model, which is a higher-dimensional generalization of the Erdős-Rényi random graph model. Recently, Knowles and Rosenthal proved that the empirical spectral distribution
of the adjacency matrix is asymptotically given by Wigner's semicircle law in a diluted regime. In this talk, I will present a central limit theorem for the linear eigenvalue statistics for test functions of polynomial growth that is of class C2 on a closed
interval. The proof is based on higher-dimensional combinatorial enumerations and concentration properties of random symmetric matrices. Furthermore, when the test function is a polynomial function, we obtain the explicit formula for the variance of the limiting
Gaussian distribution. This is joint work with Khanh Duy Trinh (Waseda University).

2024/12/12

Algebraic Geometry Seminar

13:30-15:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Chenyang Xu (Princeton University)
Irreducible symplectic varieties with a large second Betti number
[ Abstract ]
(joint with Yuchen Liu, Zhiyu Liu) We show that the Lagrangian fibration constructed by Iiiev-Manivel using intermediate Jacobians of cubic fivefolds containing a fixed cubic fourfold, admits a compactification as a terminal Q-factorial irreducible symplectic varieties. As far as I know, besides OG10, this is the second family of irreducible symplectic varieties with the second Betti number at least 24.

2024/12/11

Number Theory Seminar

17:00-18:00   Room #117 (Graduate School of Math. Sci. Bldg.)
Ryosuke Ooe (University of Tokyo)
The characteristic cycle of an l-adic sheaf on a smooth variety (Japanese)
[ Abstract ]
The characteristic cycle of an l-adic sheaf on a smooth variety over a perfect field is defined by Saito as a cycle on the cotangent bundle and the intersection with the zero section computes the Euler number. On the other hand, the characteristic cycle of an l-adic sheaf on a regular scheme in mixed characteristic is not yet defined. In this talk, I define the F-characteristic cycle of a rank one sheaf on an arithmetic surface whose intersection with the zero section computes the Swan conductor of the cohomology of the generic fiber. The definition is based on the computation of the characteristic cycle in equal characteristic by Yatagawa. I explain the rationality and the integrality of the characteristic form of an abelian character, which are necessary for the definition of the F-characteristic cycle.

2024/12/10

Tuesday Seminar on Topology

17:00-18:30   Room #ハイブリッド開催/056 (Graduate School of Math. Sci. Bldg.)
Pre-registration required. See our seminar webpage.
Shun Wakatsuki (Nagoya University)
Computation of the magnitude homology as a derived functor (JAPANESE)
[ Abstract ]
Asao-Ivanov showed that the magnitude homology of a finite metric space is isomorphic to the derived functor Tor over some ring. In this talk, I will explain an application of the theory of minimal projective resolution to this derived functor. Especially in the case of a geodetic graph, torsion-freeness and a criterion for diagonality of the magnitude homology are established. Moreover, I will give computational examples including cyclic graphs. This is a joint work with Yasuhiko Asao.
[ Reference URL ]
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html

Operator Algebra Seminars

15:00-16:30   Room #002 (Graduate School of Math. Sci. Bldg.)
Yoh Tanimoto (Univ. Rome, "Tor Vergata")
Introduction to Lean theorem prover

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

Operator Algebra Seminars

16:45-18:15   Room #002 (Graduate School of Math. Sci. Bldg.)
Maria Stella Adamo (FAU Erlangen-Nürnberg)
Osterwalder-Schrader axioms for unitary full VOAs

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

2024/12/09

Seminar on Geometric Complex Analysis

10:30-12:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Yoshiaki Suzuki (Niigata Univ.)
The spectrum of the Folland-Stein operator on some Heisenberg Bieberbach manifolds (Japanese)
[ Abstract ]
.
[ Reference URL ]
https://forms.gle/gTP8qNZwPyQyxjTj8

Tokyo Probability Seminar

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
We are having teatime from 15:15 in the common room on the second floor. Please join us.
Hayate Suda (Institute of Science Tokyo)
Scaling limits of a tagged soliton in the randomized box-ball system
[ Abstract ]
The box-ball system (BBS) is a cellular automaton that exhibits the solitonic behavior. In recent years, with the rapid progress in the study of the hydrodynamics of integrable systems, there has been a growing interest in BBS with random initial distribution. In this talk, we consider the scaling limits for a tagged soliton in the BBS starting from certain stationary distribution. This talk is based on a joint work with Stefano Olla and Makiko Sasada.

2024/12/04

Number Theory Seminar

17:00-18:00   Room #117 (Graduate School of Math. Sci. Bldg.)
Kieu Hieu Nguyen (University of Versailles Saint-Quentin)
On categorical local Langlands for GLn (English)
[ Abstract ]
Recently, Fargues-Scholze and many other people realized that there should be a categorical version which encodes great information of the local Langlands correspondence. In this talk, I will describe the objects appearing in their conjectures and explain some relations with the local Langlands correspondences for GLn.

FJ-LMI Seminar

14:00-15:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Jonathan Ditlevsen (The University of Tokyo)
Symmetry breaking operators for the pair (GL(n+1,R), GL(n,R)) (英語)
[ Abstract ]
In this talk, we construct explicit symmetry breaking operators (SBOs) between principal series representations of the group GL(n+1,R) and its subgroup GL(n,R). Using Bernstein–Sato identities, we find a holomorphic renormalization of a meromorphic family of SBOs. Finally, we identify certain differential SBOs as residues of this holomorphic family.
[ Reference URL ]
https://fj-lmi.cnrs.fr/seminars/

2024/12/03

Tuesday Seminar on Topology

17:30-18:30   Room #hybrid/056 (Graduate School of Math. Sci. Bldg.)
Pre-registration required. See our seminar webpage.
Jun-ichi Inoguchi (Hokkaido University)
Surfaces in 3-dimensional spaces and Integrable systems (JAPANESE)
[ Abstract ]
Surfaces of constant mean curvature in hyperbolic 3-space have different aspects depending on the value of mean curvature. In particular, the class of surfaces of constant mean curvature $H<1$ has no Euclidean or spherical correspondents. I would explain how to construct surface of constant mean curvature $H<1$ in hyperbolic 3-space by the method of Integrable Systems (joint work with Josef F. Dorfmeister and Shinpei Kobayashi).
[ Reference URL ]
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html

Operator Algebra Seminars

16:45-18:15   Room #122 (Graduate School of Math. Sci. Bldg.)
Valerio Proietti (Univ. Oslo)
The rational K-theory of ample groupoids

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

2024/12/02

Seminar on Geometric Complex Analysis

10:30-12:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Hideki Miyachi (Kanazawa Univ.)
Dualities in the $L^1$ and $L^\infty$-geometries in Teichm\”uller space (Japanese)
[ Reference URL ]
https://forms.gle/gTP8qNZwPyQyxjTj8

Tokyo Probability Seminar

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
We are having teatime from 15:15 in the common room on the second floor. Please join us.
Shouhei Honda (The University of Tokyo)
Weyl’s law with Ricci curvature bounded below
[ Abstract ]
Weyl’s law on a closed manifold gives an asymptotic behavior of eigenvalues of the Laplace operator in terms of the size of the manifold. It was conjectured by Luigi Ambrosio (Scuola Normale Superiore), David Tewodrose (Vrije Universiteit Brussel) and myself such that Weyl’s law is valid for Gromov-Hausdorff limit spaces with a restriction of Ricci curvature. A joint work with Xianzhe Dai (UC Santa Barbara), Jiayin Pan (UC Santa Cruz) and Guofang Wei
(UC Santa Barbara) disproved the conjecture. We will discuss about these topics in this talk.

2024/11/27

Numerical Analysis Seminar

16:30-18:00   Room #002 (Graduate School of Math. Sci. Bldg.)
Yumiharu Nakano (Institute of Science Tokyo)
Schrödinger problems and diffusion generative models (Japanese)
[ Reference URL ]
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/

FJ-LMI Seminar

14:30-15:30   Room #122 (Graduate School of Math. Sci. Bldg.)
Ali BAKLOUTI (University of Sfax)
A proof of the Zariski closure conjecture for coadjoint orbits of exponential Lie groups (英語)
[ Abstract ]
I will begin by defining the Zariski Closure Conjecture for coadjoint orbits of exponential solvable Lie groups, examining some cases that have been solved, and addressing the ongoing challenges in resolving the conjecture fully. I will then introduce new approaches to explore the relationship between generating families of primitive ideals and the set of polynomials that vanish on the associated coadjoint orbits, ultimately aiming to advance toward a solution to the conjecture.
[ Reference URL ]
https://fj-lmi.cnrs.fr/seminars/

FJ-LMI Seminar

13:30-14:30   Room #122 (Graduate School of Math. Sci. Bldg.)
Hidenori FUJIWARA (OCAMI, Kindai University)
Inductions and restrictions of unitary representations for exponential solvable Lie groups. (英語)
[ Abstract ]
Let $G = \exp \mathfrak g$ be a connected and simply connected real nilpotent Lie group with Lie algebra $\mathfrak g$, $H = \exp \mathfrak h$ an analytic subgroup of $G$ with Lie algebra $\mathfrak h$, $\chi$ a unitary character of $H$ and $\tau = \text{ind}_H^G \chi$ the monomial representation of $G$ induced from $\chi$. Let $D_{\tau}(G/H)$ be the algebra of the $G$-invariant differential operators on the line bundle over $G/H$ associated to the data $(H,\chi)$. We denote by $C_{\tau}$ the center of $D_{\tau}(G/H)$. We know that $\chi$ is written as ${\chi}_f$, where $\chi_f(\exp X) = e^{if(X)} (X \in \mathfrak h)$ with a certain $f \in {\mathfrak g}^*$ verifying $f([\mathfrak h,\mathfrak h]) = \{0\}$. Let $S(\mathfrak g)$ be the symmetric algebra of $\mathfrak g$ and ${\mathfrak a}_{\tau} = \{X + \sqrt{-1}f(X) ; X \in \mathfrak h\}.$ We regard $S(\mathfrak g)$ as the algebra of polynomial functions on ${\mathfrak g}^*$ by $X(\ell) = \sqrt{-1}\ell(X)$ for $X \in \mathfrak g, \ell \in {\mathfrak g}^*$. Now, $S(\mathfrak g)$ possesses the Poisson structure $\{,\}$ well determined by the equality $\{X,Y\} = [X,Y]$ if $X, Y$ are in $\mathfrak g$. Let us consider the algebra $(S(\mathfrak g)/S(\mathfrak g)\overline{{\mathfrak a}_{\tau}})^H$ of the $H$-invariant polynomial functions on the affine subspace ${\Gamma}_{\tau} = \{\ell \in {\mathfrak g}^* : \ell(X) = f(X), X \in \mathfrak h\}$ of ${\mathfrak g}^*$. This inherits the Poisson structure from $S(\mathfrak g)$. We denote by $Z_{\tau}$ its Poisson center. Michel Duflo asked: the two algebras $C_{\tau}$ and $Z_{\tau}$, are they isomorphic? Here we provide a positive answer to this question.
[ Reference URL ]
https://fj-lmi.cnrs.fr/seminars/

Number Theory Seminar

17:00-18:00   Room #117 (Graduate School of Math. Sci. Bldg.)
Kaito Masuzawa (University of Tokyo)
On the correspondence of simple supercuspidal representations of $\mathrm{GSp}_{2n}$ and its inner form (Japanese)
[ Abstract ]
Let $F$ be a nonarchimedean local field. The local Jacquet-Langlands correspondence is the one-to-one correspondence of essential square integrable representations of $\mathrm{GL}_n(F)$ and its inner form. It is known that this correspondence satisfies the character relation and preserves the simple supercuspidality. We assume the correspondence of simple supercuspidal representations of $\mathrm{GSp}_{2n}(F)$ and irreducible admissible representations of its inner form which satisfies the character relation. This is expected to exist by a standard argument using the theory of stable trace formula. In this talk, we show the simple supercuspidality is preserved under this correspondence. In addition, we can parametrize simple supercuspidal representations and describe the correspondence explicitly.

Lie Groups and Representation Theory

13:30-14:30   Room #122 (Graduate School of Math. Sci. Bldg.)
Joint with FJ-LMI seminar
Hidenori FUJIWARA (OCAMI, Kindai University)
Inductions and restrictions of unitary representations for exponential solvable Lie groups (English)
[ Abstract ]
Let $G=\exp{\mathfrak{g}}$ be a connected and simply connected real nilpotent Lie group with Lie algebra ${\mathfrak{g}}$, $H=\exp{\mathfrak{h}}$ an analytic subgroup of $G$ with Lie algebra ${\mathfrak{h}}$, $\chi$ a unitary character of $H$ and $\tau=\operatorname{ind}_H^G \chi$ the monomial representation of $G$ induced from $\chi$. Let $D_{\tau}(G/H)$ be the algebra of the $G$-invariant differential operators on the line bundle over $G/H$ associated to the data $(H,\chi)$. We denote by $C_{\tau}$ the center of $D_{\tau}(G/H)$. We know that $\chi$ is written as $\chi_f$, where $\chi_f(\exp X)=e^{if(X)}$ $(X∈{\mathfrak{h}})$ with a certain $f∈{\mathfrak{g}}^{\ast}$ verifying $f([{\mathfrak{h}}, {\mathfrak{h}}])=\{0\}$. Let $S({\mathfrak{g}})$ be the symmetric algebra of ${\mathfrak{g}}$ and ${\mathfrak{a}}_{\tau}=\{X+\sqrt{-1} f(X) ; X∈{\mathfrak{h}}\}$. We regard $S({\mathfrak{g}})$ as the algebra of polynomial functions on ${\mathfrak{g}}^{\ast}$ by $X(\ell)=\sqrt{-1} \ell(X)$ for $X∈{\mathfrak{g}}$, $\ell ∈{\mathfrak{g}}^{\ast}$. Now, $S({\mathfrak{g}})$ possesses the Poisson structure $\{,\}$ well determined by the equality $\{X,Y\}=[X,Y]$ if $X$,$Y$ are in ${\mathfrak{g}}$. Let us consider the algebra $(S({\mathfrak{g}})/S({\mathfrak{g}})\overline{{\mathfrak{a}}_{\tau}})^H$ of the $H$-invariant polynomial functions on the affine subspace $\Gamma_{\tau}=\{ℓ \in {\mathfrak{g}}^{\ast}:\ell(X)=f(X),X \in {\mathfrak{h}}\}$ of ${\mathfrak{g}}^{\ast}$. This inherits the Poisson structure from $S({\mathfrak{g}})$. We denote by $Z_{\tau}$ its Poisson center. Michel Duflo asked: the two algebras $C_{\tau}$ and $Z_{\tau}$, are they isomorphic? Here we provide a positive answer to this question.

Lie Groups and Representation Theory

14:30-15:30   Room #122 (Graduate School of Math. Sci. Bldg.)
Joint with FJ-LMI seminar
Ali BAKLOUTI (University of Sfax)
A proof of the Zariski closure conjecture for coadjoint orbits of exponential Lie groups (English)
[ Abstract ]
I will begin by defining the Zariski Closure Conjecture for coadjoint orbits of exponential solvable Lie groups, examining some cases that have been solved, and addressing the ongoing challenges in resolving the conjecture fully. I will then introduce new approaches to explore the relationship between generating families of primitive ideals and the set of polynomials that vanish on the associated coadjoint orbits, ultimately aiming to advance toward a solution to the conjecture.

2024/11/26

Lectures

14:30-16:30   Room #002 (Graduate School of Math. Sci. Bldg.)
Yoshihiro Ohta (Arithmer Inc., Graduate School of Mathematical Sciences the University of Tokyo, The University of Tokyo Isotope Science Center)
社会に数学を活用するArithmerの活動
[ Reference URL ]
https://sgk2005.org/

Tuesday Seminar on Topology

17:00-18:30   Room #hybrid/056 (Graduate School of Math. Sci. Bldg.)
Pre-registration required. See our seminar webpage.
Masaki Natori (The University of Tokyo)
A proof of Bott periodicity via Quot schemes and bulk-edge correspondence (JAPANESE)
[ Abstract ]
The bulk-edge correspondence refers to the phenomenon typically found in topological insulators, where the topological restriction of the bulk (interior) determines the physical state, such as electric currents, at the edge (boundary). In this talk, we focus on the formulation by G. M. Graf and M. Porta and later by S. Hayashi and provide a new proof of bulk-edge correspondence. It is more direct compared to previous approaches. Behind the proof lies the Bott periodicity of K-theory. The proof of Bott periodicity has been approached from various perspectives. We provide a new proof of Bott periodicity. In the proof, we use Quot schemes in algebraic geometry as configuration spaces.
[ Reference URL ]
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html

2024/11/25

Tokyo Probability Seminar

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
We are having teatime from 15:15 in the common room on the second floor. Please join us.
Leon Frober (Grand Valley State University)
Free energy and ground state of the spiked SSK spin-glass model
[ Abstract ]
Spin-glasses are essentially mathematical models of particle interactions, and were originally describing magnetic states characterized by randomness in condensed matter physics. Due to the versatility of these types of models, however, they are now studied much more broadly for various complex systems such as statistical inference problems, weather/climate models or even neural networks. In this talk we will lay out the basic concepts of spin-glass models, while then focusing on the spiked SSK variant and its free energy as well as ground state energy. Furthermore we will discuss how one can determine these quantities including their lower order fluctuations with a so called "TAP approach" that was in this comprehensive form introduced in 2016 by N. Kistler and D. Belius, and what its benefits are compared to the earlier established "Parisi approach".

2024/11/22

Algebraic Geometry Seminar

13:30-15:00   Room #118 (Graduate School of Math. Sci. Bldg.)
Hiroshi Iritani (Kyoto University)
Quantum cohomology of blowups
[ Abstract ]
I will discuss a decomposition theorem for the quantum cohomology of a smooth projective variety blown up along a smooth subvariety. I will start with a general relationship between decomposition of quantum cohomology and extremal contractions, and then specialize to the case of blowups. Applications to birational geometry of this result have been announced by Katzarkov, Kontsevich, Pantev and Yu.

< Previous 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194 Next >