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Seminar information archive
Seminar information archive ～05/13｜Today's seminar 05/14 | Future seminars 05/15～
Information Mathematics Seminar
16:50-18:35 Room #128 (Graduate School of Math. Sci. Bldg.)
Tatsuaki Okamoto (NTT)
Security, construction, and proof of public-key encryption (1) (Japanese)
Tatsuaki Okamoto (NTT)
Security, construction, and proof of public-key encryption (1) (Japanese)
[ Abstract ]
Explanation on security, construction, and proof of public-key encryption
Explanation on security, construction, and proof of public-key encryption
2023/05/17
Number Theory Seminar
17:00-18:00 Room #117 (Graduate School of Math. Sci. Bldg.)
Ken Sato (Tokyo Institute of Technology)
Indecomposable higher Chow cycles on Kummer surfaces (日本語)
Ken Sato (Tokyo Institute of Technology)
Indecomposable higher Chow cycles on Kummer surfaces (日本語)
[ Abstract ]
The higher Chow group $\mathrm{CH}^p(X,q)$ introduced by Bloch is a generalization of the classical Chow groups. It satisfies many interesting properties, but its structure is still mysterious for almost all varieties when $p$ is greater than 1. In this talk, I will explain the explicit construction of higher Chow cycles in $\mathrm{CH}^2(X,1)$ on a family of Kummer surfaces. By computing their images under the Beilinson regulator map, in very general cases, these cycles generate at least rank 18 subgroup of $\mathrm{CH}^2(X,1)_{\mathrm{ind}}$, which is the quotient of $\mathrm{CH}^2(X,1)$ by the images of the intersection product maps. To compute the images under the regulator map, we use automorphisms of the family and the explicit description of the action of the automorphisms on the Picard-Fuchs differential equations of the family.
The higher Chow group $\mathrm{CH}^p(X,q)$ introduced by Bloch is a generalization of the classical Chow groups. It satisfies many interesting properties, but its structure is still mysterious for almost all varieties when $p$ is greater than 1. In this talk, I will explain the explicit construction of higher Chow cycles in $\mathrm{CH}^2(X,1)$ on a family of Kummer surfaces. By computing their images under the Beilinson regulator map, in very general cases, these cycles generate at least rank 18 subgroup of $\mathrm{CH}^2(X,1)_{\mathrm{ind}}$, which is the quotient of $\mathrm{CH}^2(X,1)$ by the images of the intersection product maps. To compute the images under the regulator map, we use automorphisms of the family and the explicit description of the action of the automorphisms on the Picard-Fuchs differential equations of the family.
2023/05/16
Operator Algebra Seminars
16:45-18:15 Room #126 (Graduate School of Math. Sci. Bldg.)
Mizuki Oikawa (Univ. Tokyo)
Group actions on bimodules and equivariant $\alpha$-induction
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Mizuki Oikawa (Univ. Tokyo)
Group actions on bimodules and equivariant $\alpha$-induction
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Numerical Analysis Seminar
16:30-18:00 Room #002 (Graduate School of Math. Sci. Bldg.)
Yuuki Shimizu (The University of Tokyo)
Numerical analysis of the Plateau problem by the method of fundamental solutions (Japanese)
[ Reference URL ]
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
Yuuki Shimizu (The University of Tokyo)
Numerical analysis of the Plateau problem by the method of fundamental solutions (Japanese)
[ Reference URL ]
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
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.
Mayuko Yamashita (Kyoto University)
Anderson self-duality of topological modular forms and heretoric string theory (JAPANESE)
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Pre-registration required. See our seminar webpage.
Mayuko Yamashita (Kyoto University)
Anderson self-duality of topological modular forms and heretoric string theory (JAPANESE)
[ Abstract ]
Topological Modular Forms (TMF) is an E-infinity ring spectrum which is conjectured by Stolz-Teichner to classify two-dimensional supersymmetric quantum field theories in physics. In the previous work with Y. Tachikawa, we proved the vanishing of anomalies in heterotic string theory mathematically by using TMF. In this talk, I explain our recent update on the previous work. Because of the vanishing result, we can consider a secondary transformation of spectra, which is shown to coincide with the Anderson self-duality morphism of TMF. This allows us to detect subtle torsion phenomena in TMF by differential-geometric ways.
[ Reference URL ]Topological Modular Forms (TMF) is an E-infinity ring spectrum which is conjectured by Stolz-Teichner to classify two-dimensional supersymmetric quantum field theories in physics. In the previous work with Y. Tachikawa, we proved the vanishing of anomalies in heterotic string theory mathematically by using TMF. In this talk, I explain our recent update on the previous work. Because of the vanishing result, we can consider a secondary transformation of spectra, which is shown to coincide with the Anderson self-duality morphism of TMF. This allows us to detect subtle torsion phenomena in TMF by differential-geometric ways.
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Tokyo-Nagoya Algebra Seminar
15:00-16:30 Online
Antoine de Saint Germain (University of Hong Kong)
Cluster-additive functions and frieze patterns with coefficients (English)
http://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html
Antoine de Saint Germain (University of Hong Kong)
Cluster-additive functions and frieze patterns with coefficients (English)
[ Abstract ]
In his study of combinatorial features of cluster categories and cluster-tilted algebras, Ringel introduced an analogue of additive functions of stable translation quivers called cluster-additive functions.
In the first part of this talk, we will define cluster-additive functions associated to any acyclic mutation matrix, relate them to mutations of the cluster X variety, and realise their values as certain compatibility degrees between functions on the cluster A variety associated to the Langlands dual mutation matrix (in accordance with the philosophy of Fock-Goncharov). This is based on joint work with Peigen Cao and Jiang-Hua Lu. In the second part of this talk, we will introduce the notion of frieze patterns with coefficients based on joint work with Min Huang and Jiang-Hua Lu. We will then discuss their connection with cluster-additive functions.
ミーティングID: 815 4247 1556
パスコード: 742240
[ Reference URL ]In his study of combinatorial features of cluster categories and cluster-tilted algebras, Ringel introduced an analogue of additive functions of stable translation quivers called cluster-additive functions.
In the first part of this talk, we will define cluster-additive functions associated to any acyclic mutation matrix, relate them to mutations of the cluster X variety, and realise their values as certain compatibility degrees between functions on the cluster A variety associated to the Langlands dual mutation matrix (in accordance with the philosophy of Fock-Goncharov). This is based on joint work with Peigen Cao and Jiang-Hua Lu. In the second part of this talk, we will introduce the notion of frieze patterns with coefficients based on joint work with Min Huang and Jiang-Hua Lu. We will then discuss their connection with cluster-additive functions.
ミーティングID: 815 4247 1556
パスコード: 742240
http://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html
Lie Groups and Representation Theory
17:00-18:00 Room #online (Graduate School of Math. Sci. Bldg.)
Hiroyoshi TAMORI (Shibaura institute of technology)
Integral expression of the $(k,a)$-generalized Laguerre semigroup
(Japanese)
Hiroyoshi TAMORI (Shibaura institute of technology)
Integral expression of the $(k,a)$-generalized Laguerre semigroup
(Japanese)
[ Abstract ]
The $(k,a)$-generalized Laguerre semigroup was introduced by Ben
Sa\"{\i}d--Kobayashi-{\O}rsted as an interpolation of the Hermite semigroup (the k=0, a=2 case) and the Laguerre semigroup (the k=0, a=1 case). Based on a joint work with Kouichi Taira (Ritsumeikan University), I will explain an integral expression of the semigroup and an upper estimate of the integral kernel, which leads to Strichartz estimates for operators $|x|^{2-a}\Delta_{k}-|x|^a$ and $|x|^{2-a}\Delta_{k}$ ($\Delta_k$ denotes the Dunkl Laplacian) under some condition on the deformation parameter $(k,a)$.
The $(k,a)$-generalized Laguerre semigroup was introduced by Ben
Sa\"{\i}d--Kobayashi-{\O}rsted as an interpolation of the Hermite semigroup (the k=0, a=2 case) and the Laguerre semigroup (the k=0, a=1 case). Based on a joint work with Kouichi Taira (Ritsumeikan University), I will explain an integral expression of the semigroup and an upper estimate of the integral kernel, which leads to Strichartz estimates for operators $|x|^{2-a}\Delta_{k}-|x|^a$ and $|x|^{2-a}\Delta_{k}$ ($\Delta_k$ denotes the Dunkl Laplacian) under some condition on the deformation parameter $(k,a)$.
2023/05/15
Seminar on Geometric Complex Analysis
10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Yuya Takeuchi (Tsukuba Univeristy)
$\mathcal{I}'$-curvatures and the Hirachi conjecture (Japanese)
https://u-tokyo-ac-jp.zoom.us/meeting/register/tZEqceqsrTIjEtRxenSMdPogvCxlWzAogj5A
Yuya Takeuchi (Tsukuba Univeristy)
$\mathcal{I}'$-curvatures and the Hirachi conjecture (Japanese)
[ Abstract ]
Hirachi conjecture deals with a relation between the integrals of local pseudo-Hermitian invariants and global CR invariants. This is a CR analogue of the Deser-Schwimmer conjceture, which was proved by Alexakis. In this talk, I would like to explain some results on the Hirachi conjecture. In particular, I'll introduce the $\mathcal{I}'$-curvatures and prove that these produce counterexamples to the Hirachi conjecture in higher dimensions. This talk is based on joint work with Jeffrey S. Case.
[ Reference URL ]Hirachi conjecture deals with a relation between the integrals of local pseudo-Hermitian invariants and global CR invariants. This is a CR analogue of the Deser-Schwimmer conjceture, which was proved by Alexakis. In this talk, I would like to explain some results on the Hirachi conjecture. In particular, I'll introduce the $\mathcal{I}'$-curvatures and prove that these produce counterexamples to the Hirachi conjecture in higher dimensions. This talk is based on joint work with Jeffrey S. Case.
https://u-tokyo-ac-jp.zoom.us/meeting/register/tZEqceqsrTIjEtRxenSMdPogvCxlWzAogj5A
Tokyo Probability Seminar
17:00-18:30 Room #126 (Graduate School of Math. Sci. Bldg.)
岡田いず海 (千葉大学)
Capacity of the range of random walk (JAPANESE)
岡田いず海 (千葉大学)
Capacity of the range of random walk (JAPANESE)
[ Abstract ]
We study the capacity of the range of a simple random walk in three and higher dimensions. It is known that the order of the capacity of the random walk range in n dimensions is similar to that of the volume of the random walk range in n-2 dimensions. We show that this correspondence breaks down for the law of the iterated logarithm for the capacity of the random walk range in three dimensions. We also prove the law of the iterated logarithm in higher dimensions. This is joint work with Amir Dembo.
We study the capacity of the range of a simple random walk in three and higher dimensions. It is known that the order of the capacity of the random walk range in n dimensions is similar to that of the volume of the random walk range in n-2 dimensions. We show that this correspondence breaks down for the law of the iterated logarithm for the capacity of the random walk range in three dimensions. We also prove the law of the iterated logarithm in higher dimensions. This is joint work with Amir Dembo.
2023/05/11
Information Mathematics Seminar
16:50-18:35 Room #128 (Graduate School of Math. Sci. Bldg.)
Tatsuaki Okamoto (NTT)
The security definition and proof of symmetric key encryption and public key encryption (Japanese)
Tatsuaki Okamoto (NTT)
The security definition and proof of symmetric key encryption and public key encryption (Japanese)
[ Abstract ]
Explanation of the security definition and proof of symmetric key encryption and public key encryption
Explanation of the security definition and proof of symmetric key encryption and public key encryption
2023/05/10
Number Theory Seminar
17:00-18:00 Room #117 (Graduate School of Math. Sci. Bldg.)
Guy Henniart (Paris-Sud University)
Swan exponent of Galois representations and fonctoriality for classical groups over p-adic fields (English)
Guy Henniart (Paris-Sud University)
Swan exponent of Galois representations and fonctoriality for classical groups over p-adic fields (English)
[ Abstract ]
This is joint work with Masao Oi in Kyoto. Let F be a p-adic field for some prime number p,
F^ac an algebraic closure of F, and G_F the Galois group of F^ac/F. A continuous finite dimensional
representation σ (on a complex vector space W) has a Swan exponent s(σ), a non-negative integer
which measures how "wildly ramified" σ is. Langlands functoriality makes it of interest
to compare s(σ) and s(r o σ) when r is an algebraic representation of Aut_C(W). The first cases
for r are the determinant, the adjoint representation, the symmetric square representation and
the alternating square representation. I shall give some relations (inequalities mostly, with
equality in interesting cases) between the Swan exponents of those representations r o σ. I shall
also indicate how such relations can be used to explicit the local Langlands correspondence of
Arthur for some simple cuspidal representations of split classical groups over F.
This is joint work with Masao Oi in Kyoto. Let F be a p-adic field for some prime number p,
F^ac an algebraic closure of F, and G_F the Galois group of F^ac/F. A continuous finite dimensional
representation σ (on a complex vector space W) has a Swan exponent s(σ), a non-negative integer
which measures how "wildly ramified" σ is. Langlands functoriality makes it of interest
to compare s(σ) and s(r o σ) when r is an algebraic representation of Aut_C(W). The first cases
for r are the determinant, the adjoint representation, the symmetric square representation and
the alternating square representation. I shall give some relations (inequalities mostly, with
equality in interesting cases) between the Swan exponents of those representations r o σ. I shall
also indicate how such relations can be used to explicit the local Langlands correspondence of
Arthur for some simple cuspidal representations of split classical groups over F.
Algebraic Geometry Seminar
13:30-15:00 Room #ハイブリッド開催/056 (Graduate School of Math. Sci. Bldg.)
Jakub Witaszek (Princeton University)
Singularities in mixed characteristic via the Riemann-Hilbert correspondence (English)
Jakub Witaszek (Princeton University)
Singularities in mixed characteristic via the Riemann-Hilbert correspondence (English)
[ Abstract ]
In my talk, I will start by reviewing how various properties of characteristic zero singularities can be understood topologically by ways of the Riemann-Hilbert correspondence. After that, I will explain how similar ideas can be applied in the study of mixed characteristic singularities. This is based on a joint work (in progress) with Bhargav Bhatt, Linquan Ma, Zsolt Patakfalvi, Karl Schwede, Kevin Tucker, and Joe Waldron.
In my talk, I will start by reviewing how various properties of characteristic zero singularities can be understood topologically by ways of the Riemann-Hilbert correspondence. After that, I will explain how similar ideas can be applied in the study of mixed characteristic singularities. This is based on a joint work (in progress) with Bhargav Bhatt, Linquan Ma, Zsolt Patakfalvi, Karl Schwede, Kevin Tucker, and Joe Waldron.
2023/05/09
Operator Algebra Seminars
16:45-18:15 Room #126 (Graduate School of Math. Sci. Bldg.)
Yoh Tanimoto (Univ Rome, Tor Vergata)
Lattice Green functions (after Balaban/Dimock) (English)
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Yoh Tanimoto (Univ Rome, Tor Vergata)
Lattice Green functions (after Balaban/Dimock) (English)
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Tuesday Seminar on Topology
17:00-18:00 Online
Pre-registration required. See our seminar webpage.
Michihisa Wakui (Kansai University)
Knots and frieze patterns (JAPANESE)
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Pre-registration required. See our seminar webpage.
Michihisa Wakui (Kansai University)
Knots and frieze patterns (JAPANESE)
[ Abstract ]
(joint work with Prof. Takeyoshi Kogiso (Josai University)) In the early 1970s, Conway and Coxeter introduced frieze patterns of positive integers arranged under the unimodular rule ad-bc=1, and showed that they are classified by triangulations of convex polygons. Currently, the frieze patterns by Conway and Coxeter are spotlighted in connection with cluster algebras which are introduced by Fomin and Zelevinsky in the early 2000s.
Working with Takeyoshi Kogiso in Josai University the speaker study on relationship between rational links and Conway-Coxeter friezes through ancestor triangles of rational numbers introduced by Shuji Yamada in Kyoto Sangyo University, and show that rational links are characterized by Conway-Coxeter friezes of zigzag type. At nearly the same time Morier-Genoud and Ovsienko also introduce the concept of q-deformation of rational numbers based on continued fraction expansions, and derive closely related results to our research. In this seminar we will talk about an outline of these results.
[ Reference URL ](joint work with Prof. Takeyoshi Kogiso (Josai University)) In the early 1970s, Conway and Coxeter introduced frieze patterns of positive integers arranged under the unimodular rule ad-bc=1, and showed that they are classified by triangulations of convex polygons. Currently, the frieze patterns by Conway and Coxeter are spotlighted in connection with cluster algebras which are introduced by Fomin and Zelevinsky in the early 2000s.
Working with Takeyoshi Kogiso in Josai University the speaker study on relationship between rational links and Conway-Coxeter friezes through ancestor triangles of rational numbers introduced by Shuji Yamada in Kyoto Sangyo University, and show that rational links are characterized by Conway-Coxeter friezes of zigzag type. At nearly the same time Morier-Genoud and Ovsienko also introduce the concept of q-deformation of rational numbers based on continued fraction expansions, and derive closely related results to our research. In this seminar we will talk about an outline of these results.
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
2023/05/08
Seminar on Geometric Complex Analysis
10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Hisashi Kasuya (Osaka Univeristy)
Non-Kähler Hodge theory and resolutions of cyclic orbifolds (日本語)
https://u-tokyo-ac-jp.zoom.us/meeting/register/tZEqceqsrTIjEtRxenSMdPogvCxlWzAogj5A
Hisashi Kasuya (Osaka Univeristy)
Non-Kähler Hodge theory and resolutions of cyclic orbifolds (日本語)
[ Abstract ]
This talk is based on the joint works with Jonas Stelzig (LMU München). We discuss the Hodge theory of non-Kähler compact complex manifolds. In this term, we think several types of compact complex manifolds and compact Kähler manifolds are considered as the "simplest”. We give a way of constructing simply connected compact complex non-Kähler manifolds of certain types by using resolutions of cyclic orbifolds.
[ Reference URL ]This talk is based on the joint works with Jonas Stelzig (LMU München). We discuss the Hodge theory of non-Kähler compact complex manifolds. In this term, we think several types of compact complex manifolds and compact Kähler manifolds are considered as the "simplest”. We give a way of constructing simply connected compact complex non-Kähler manifolds of certain types by using resolutions of cyclic orbifolds.
https://u-tokyo-ac-jp.zoom.us/meeting/register/tZEqceqsrTIjEtRxenSMdPogvCxlWzAogj5A
Tokyo Probability Seminar
17:00-18:30 Room #126 (Graduate School of Math. Sci. Bldg.)
新井裕太 (千葉商科大学)
On the Chapman-Kolmogorov equation for LPP (JAPANESE)
新井裕太 (千葉商科大学)
On the Chapman-Kolmogorov equation for LPP (JAPANESE)
[ Abstract ]
KPZ普遍クラスに属するいくつかのモデルにおいて，その推移確率等が複素積分形の関数で書き表せることが知られている．しかしながら，複素積分を用いた計算は複雑となることも多く，KPZ普遍クラスに属するモデルにとって重要な確率論的性質を証明するのが困難となっていた．近年，この問題を解決するものとして対称多項式等を用いた組合せ論的手法に注目が集まってきている．本講演では，最先端の組合せ論的アプローチを用いることで，KPZ普遍クラスの基礎的なモデルであるLast Passage Percolation（LPP）において， Chapman-Kolmogorov equationが容易に得られることを紹介する.
KPZ普遍クラスに属するいくつかのモデルにおいて，その推移確率等が複素積分形の関数で書き表せることが知られている．しかしながら，複素積分を用いた計算は複雑となることも多く，KPZ普遍クラスに属するモデルにとって重要な確率論的性質を証明するのが困難となっていた．近年，この問題を解決するものとして対称多項式等を用いた組合せ論的手法に注目が集まってきている．本講演では，最先端の組合せ論的アプローチを用いることで，KPZ普遍クラスの基礎的なモデルであるLast Passage Percolation（LPP）において， Chapman-Kolmogorov equationが容易に得られることを紹介する.
2023/05/02
Operator Algebra Seminars
16:45-18:15 Room #126 (Graduate School of Math. Sci. Bldg.)
Ayoub Hafid (Univ. Tokyo)
KK-theory, localization algebras, and approximation
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Ayoub Hafid (Univ. Tokyo)
KK-theory, localization algebras, and approximation
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Operator Algebra Seminars
16:45-18:15 Room #126 (Graduate School of Math. Sci. Bldg.)
Ayoub Hafid (Univ. Tokyo)
KK-theory, localization algebras, and approximation
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Ayoub Hafid (Univ. Tokyo)
KK-theory, localization algebras, and approximation
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
2023/04/28
Colloquium
15:30-16:30 Hybrid
If you do not belong to Graduate School of Mathematical Sciences, the University of Tokyo, please take part online [Reference URL]
Kazuo Habiro (Graduate School of Mathematical Sciences, the University of Tokyo)
On quantum topology (日本語)
https://u-tokyo-ac-jp.zoom.us/meeting/register/tZIkc-Cvrz4oHNXj_kafJqhU6ZFWCABqgojM
If you do not belong to Graduate School of Mathematical Sciences, the University of Tokyo, please take part online [Reference URL]
Kazuo Habiro (Graduate School of Mathematical Sciences, the University of Tokyo)
On quantum topology (日本語)
[ Abstract ]
I started my research from surgery theory of knots and 3-manifolds. This is related to finite type invariants, which was studied intensively at that time. I obtained a result which characterises the information that is carried by finite type invariants in terms of clasper surgery. After that, I have studied quantum invariants of integral homology spheres, Kirby calculus of framed links, quantum invariants of bottom tangles, functorialization of Le-Murakami-Ohtsuki invariants, quantum fundamental groups and quantum representation variety of 3-manifolds, traces of categorified quantum groups, etc. I would like to reflect on these studies and also discuss future prospects.
[ Reference URL ]I started my research from surgery theory of knots and 3-manifolds. This is related to finite type invariants, which was studied intensively at that time. I obtained a result which characterises the information that is carried by finite type invariants in terms of clasper surgery. After that, I have studied quantum invariants of integral homology spheres, Kirby calculus of framed links, quantum invariants of bottom tangles, functorialization of Le-Murakami-Ohtsuki invariants, quantum fundamental groups and quantum representation variety of 3-manifolds, traces of categorified quantum groups, etc. I would like to reflect on these studies and also discuss future prospects.
https://u-tokyo-ac-jp.zoom.us/meeting/register/tZIkc-Cvrz4oHNXj_kafJqhU6ZFWCABqgojM
Tokyo-Nagoya Algebra Seminar
13:00-14:30 Online
Please see the reference URL for details on the online seminar.
Takumi Otani (Osaka Univeristy)
Full exceptional collections associated with Bridgeland stability conditions (Japanese)
http://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html
Please see the reference URL for details on the online seminar.
Takumi Otani (Osaka Univeristy)
Full exceptional collections associated with Bridgeland stability conditions (Japanese)
[ Abstract ]
The space of Bridgeland stability conditions on a triangulated category is important in mirror symmetry and many people develop various techniques to study it. In order to study the homotopy type of the space of stability conditions, Macri studied stability conditions associated with full exceptional collections. Based on his work, Dimitrov-Katzarkov introduced the notion of a full σ-exceptional collection for a stability condition σ.
In this talk, I will explain the relationship between full exceptional collections and stability conditions and some properties. I will also talk about the existence of full σ-exceptional collections for the derived category of an acyclic quiver.
[ Reference URL ]The space of Bridgeland stability conditions on a triangulated category is important in mirror symmetry and many people develop various techniques to study it. In order to study the homotopy type of the space of stability conditions, Macri studied stability conditions associated with full exceptional collections. Based on his work, Dimitrov-Katzarkov introduced the notion of a full σ-exceptional collection for a stability condition σ.
In this talk, I will explain the relationship between full exceptional collections and stability conditions and some properties. I will also talk about the existence of full σ-exceptional collections for the derived category of an acyclic quiver.
http://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html
Algebraic Geometry Seminar
13:30-15:00 Room #ハイブリッド開催/117 (Graduate School of Math. Sci. Bldg.)
Taro Yoshino (Tokyo)
On the degree of irrationality of complete intersections (Japanese )
Taro Yoshino (Tokyo)
On the degree of irrationality of complete intersections (Japanese )
[ Abstract ]
The degree of irrationality of a variety X is the minimum degree of a dominant, generically finite rational map from X to a rational variety. This invariant gives a measure of how far X is from being rational. There were some varieties whose degree of irrationality was computed. For example, in 2017, Bastianelli, De Poi, Ein, Lazarsfeld, and Ullery computed the degree of irrationality of very general hypersurfaces of general type by using the positivity of the canonical line bundle. On the other hand, in 2020, Chen and Stapleton obtained the lower bound of the degree of irrationality of very general Fano hypersurfaces by using the reduction of modulo p.
In this talk, we will show that we can obtain the lower bound of the degree of irrationality of very general Fano complete intersections. For obtaining the bound, we make a minor adjustment to Chen--Stapleton's method using the trace map of differential modules.
This talk is based on joint work with Lucas Braune.
The degree of irrationality of a variety X is the minimum degree of a dominant, generically finite rational map from X to a rational variety. This invariant gives a measure of how far X is from being rational. There were some varieties whose degree of irrationality was computed. For example, in 2017, Bastianelli, De Poi, Ein, Lazarsfeld, and Ullery computed the degree of irrationality of very general hypersurfaces of general type by using the positivity of the canonical line bundle. On the other hand, in 2020, Chen and Stapleton obtained the lower bound of the degree of irrationality of very general Fano hypersurfaces by using the reduction of modulo p.
In this talk, we will show that we can obtain the lower bound of the degree of irrationality of very general Fano complete intersections. For obtaining the bound, we make a minor adjustment to Chen--Stapleton's method using the trace map of differential modules.
This talk is based on joint work with Lucas Braune.
2023/04/27
Information Mathematics Seminar
16:50-18:35 Room #128 (Graduate School of Math. Sci. Bldg.)
Tatsuaki Okamoto (NTT)
The basics of cryptography II (Japanese)
Tatsuaki Okamoto (NTT)
The basics of cryptography II (Japanese)
[ Abstract ]
Explanation of the basics of cryptography
Explanation of the basics of cryptography
2023/04/26
Number Theory Seminar
18:00-19:30 Room #117 (Graduate School of Math. Sci. Bldg.)
Live transmission from IHES, Warning: Start time is one hour later than usual.
Dustin Clausen (Institut des Hautes Études Scientifiques)
A Conjectural Reciprocity Law for Realizations of Motives
https://indico.math.cnrs.fr/event/9634/
Live transmission from IHES, Warning: Start time is one hour later than usual.
Dustin Clausen (Institut des Hautes Études Scientifiques)
A Conjectural Reciprocity Law for Realizations of Motives
[ Abstract ]
A motive over a scheme S is a bit of linear algebra which is supposed to "universally" capture the cohomology of smooth proper S-schemes. Motives can be studied via various "realizations", which are objects of more concrete linear algebraic categories attached to S. It is known that over certain S, these different realizations are related to one another via comparison isomorphisms, as in Hodge theory. In this talk, I will try to explain that for completely general S, there is a much more subtle kind of relationship between these realizations, which takes a similar form to classical reciprocity laws in number theory.
[ Reference URL ]A motive over a scheme S is a bit of linear algebra which is supposed to "universally" capture the cohomology of smooth proper S-schemes. Motives can be studied via various "realizations", which are objects of more concrete linear algebraic categories attached to S. It is known that over certain S, these different realizations are related to one another via comparison isomorphisms, as in Hodge theory. In this talk, I will try to explain that for completely general S, there is a much more subtle kind of relationship between these realizations, which takes a similar form to classical reciprocity laws in number theory.
https://indico.math.cnrs.fr/event/9634/
2023/04/25
Tuesday Seminar on Topology
17:00-18:00 Online
Pre-registration required. See our seminar webpage.
Hiraku Nozawa (Ritsumeikan University)
Harmonic measures and rigidity of surface group actions on the circle (JAPANESE)
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Pre-registration required. See our seminar webpage.
Hiraku Nozawa (Ritsumeikan University)
Harmonic measures and rigidity of surface group actions on the circle (JAPANESE)
[ Abstract ]
We study rigidity properties of surface group actions on the circle via harmonic measures on the suspension bundles, which are measures invariant under the heat diffusion along leaves. We will explain a curvature estimate and a Gauss-Bonnet formula for an S^1-connection obtained by taking the average of the flat connection on the suspension bundle with respect to a harmonic measure. As consequences, we give a precise description of the harmonic measure on suspension foliations with maximal Euler number and an alternative proof of semiconjugacy rigidity theorems of Matsumoto and Burger-Iozzi-Wienhard for actions with maximal Euler number. This is joint work with Masanori Adachi and Yoshifumi Matsuda.
[ Reference URL ]We study rigidity properties of surface group actions on the circle via harmonic measures on the suspension bundles, which are measures invariant under the heat diffusion along leaves. We will explain a curvature estimate and a Gauss-Bonnet formula for an S^1-connection obtained by taking the average of the flat connection on the suspension bundle with respect to a harmonic measure. As consequences, we give a precise description of the harmonic measure on suspension foliations with maximal Euler number and an alternative proof of semiconjugacy rigidity theorems of Matsumoto and Burger-Iozzi-Wienhard for actions with maximal Euler number. This is joint work with Masanori Adachi and Yoshifumi Matsuda.
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Numerical Analysis Seminar
16:30-18:00 Room #002 (Graduate School of Math. Sci. Bldg.)
Taihei Oki (The University of Tokyo)
Combinatorial preprocessing methods for differential-algebraic equations (Japanese)
[ Reference URL ]
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
Taihei Oki (The University of Tokyo)
Combinatorial preprocessing methods for differential-algebraic equations (Japanese)
[ Reference URL ]
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
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