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Seminar information archive
Seminar information archive ～04/17｜Today's seminar 04/18 | Future seminars 04/19～
2023/10/19
Information Mathematics Seminar
16:50-18:35 Room #128 (Graduate School of Math. Sci. Bldg.)
Katsuyuki Takashima (Waseda Univ.)
Mathematical Aspects of Lattice-Based Cryptography (Japanese)
Katsuyuki Takashima (Waseda Univ.)
Mathematical Aspects of Lattice-Based Cryptography (Japanese)
[ Abstract ]
I will explain mathematical aspects of lattice-based cryptography.
I will explain mathematical aspects of lattice-based cryptography.
2023/10/18
Number Theory Seminar
17:00-18:00 Room #117 (Graduate School of Math. Sci. Bldg.)
Wansu Kim (KAIST/University of Tokyo)
On Igusa varieties (English)
Wansu Kim (KAIST/University of Tokyo)
On Igusa varieties (English)
[ Abstract ]
In this talk, we construct Igusa varieties and study some basic properties in the setting of abelian-type Shimura varieties, as well as in the analogous setting for function fields (over shtuka spaces). The is joint work with Paul Hamacher.
In this talk, we construct Igusa varieties and study some basic properties in the setting of abelian-type Shimura varieties, as well as in the analogous setting for function fields (over shtuka spaces). The is joint work with Paul Hamacher.
2023/10/17
Numerical Analysis Seminar
16:30-18:00 Room #002 (Graduate School of Math. Sci. Bldg.)
Makoto Okumura (Konan University)
Structure-preserving schemes for the Cahn-Hilliard equation with dynamic boundary conditions in two spatial dimensions (Japanese)
[ Reference URL ]
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
Makoto Okumura (Konan University)
Structure-preserving schemes for the Cahn-Hilliard equation with dynamic boundary conditions in two spatial dimensions (Japanese)
[ Reference URL ]
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
Tuesday Seminar on Topology
17:00-18:00 Online
Pre-registration required. See our seminar webpage.
Shunsuke Kano (MathCCS, Tohoku University)
Train track combinatorics and cluster algebras (JAPANESE)
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Pre-registration required. See our seminar webpage.
Shunsuke Kano (MathCCS, Tohoku University)
Train track combinatorics and cluster algebras (JAPANESE)
[ Abstract ]
The concepts of train track was introduced by W. P. Thurston to study the measured foliations/laminations and the pseudo-Anosov mapping classes on a surface. In this talk, we translate some concepts of train tracks into the language of cluster algebras using the tropicalization of Goncharov--Shen's potential function. Using this, we translate a combinatorial property of a train track associated with a pseudo-Anosov mapping class into the combinatorial property in cluster algebras, called the sign stability which was introduced by Tsukasa Ishibashi and the speaker.
[ Reference URL ]The concepts of train track was introduced by W. P. Thurston to study the measured foliations/laminations and the pseudo-Anosov mapping classes on a surface. In this talk, we translate some concepts of train tracks into the language of cluster algebras using the tropicalization of Goncharov--Shen's potential function. Using this, we translate a combinatorial property of a train track associated with a pseudo-Anosov mapping class into the combinatorial property in cluster algebras, called the sign stability which was introduced by Tsukasa Ishibashi and the speaker.
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Operator Algebra Seminars
16:45-18:15 Room #128 (Graduate School of Math. Sci. Bldg.)
Fuyuta Komura (RIKEN)
$*$-homomorphisms between groupoid C$^*$-algebras
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Fuyuta Komura (RIKEN)
$*$-homomorphisms between groupoid C$^*$-algebras
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
2023/10/16
Algebraic Geometry Seminar
14:00-15:30 Room #002 (Graduate School of Math. Sci. Bldg.)
Lena Ji (University of Michigan)
Symmetries of Fano varieties
Lena Ji (University of Michigan)
Symmetries of Fano varieties
[ Abstract ]
Prokhorov and Shramov proved that the BAB conjecture (which Birkar later proved) implies the uniform Jordan property for automorphism groups of complex Fano varieties of fixed dimension. This property in particular gives an upper bound on the size of semi-simple groups (meaning those with no non-trivial normal abelian subgroups) acting faithfully on n-dimensional complex Fano varieties, and this bound only depends on n. In this talk, we investigate the consequences of a large action by a particular semi-simple group: the symmetric group. This work is joint with Louis Esser and Joaquín Moraga.
Prokhorov and Shramov proved that the BAB conjecture (which Birkar later proved) implies the uniform Jordan property for automorphism groups of complex Fano varieties of fixed dimension. This property in particular gives an upper bound on the size of semi-simple groups (meaning those with no non-trivial normal abelian subgroups) acting faithfully on n-dimensional complex Fano varieties, and this bound only depends on n. In this talk, we investigate the consequences of a large action by a particular semi-simple group: the symmetric group. This work is joint with Louis Esser and Joaquín Moraga.
Seminar on Geometric Complex Analysis
10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Hajime Tsuji (Sophia University)
The limit of Kähler-Ricci flows
https://u-tokyo-ac-jp.zoom.us/meeting/register/tZEqceqsrTIjEtRxenSMdPogvCxlWzAogj5A
Hajime Tsuji (Sophia University)
The limit of Kähler-Ricci flows
[ Abstract ]
In this talk, I would like to present the (normalized) limit of Kähler-Ricci flows for compact Kähler manifolds with intermediate Kodaira dimesion under the condition that the canonical bundle is abundant.
[ Reference URL ]In this talk, I would like to present the (normalized) limit of Kähler-Ricci flows for compact Kähler manifolds with intermediate Kodaira dimesion under the condition that the canonical bundle is abundant.
https://u-tokyo-ac-jp.zoom.us/meeting/register/tZEqceqsrTIjEtRxenSMdPogvCxlWzAogj5A
2023/10/12
Tokyo-Nagoya Algebra Seminar
10:30-12:00 Online
Xin Ren (Kansai University)
q-deformed rational numbers, Farey sum and a 2-Calabi-Yau category of A_2 quiver (English)
http://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html
Xin Ren (Kansai University)
q-deformed rational numbers, Farey sum and a 2-Calabi-Yau category of A_2 quiver (English)
[ Abstract ]
Let q be a positive real number. The left and right q-deformed rational numbers were introduced by Bapat, Becker and Licata via regular continued fractions, and the right q-deformed rational number is exactly q-deformed rational number considered by Morier-Genoud and Ovsienko, when q is a formal parameter. They gave a homological interpretation for left and right q-deformed rational numbers by considering a special 2-Calabi–Yau category associated to the A_2 quiver.
In this talk, we begin by introducing the above definitions and related results. Then we give a formula for computing the q-deformed Farey sum of the left q-deformed rational numbers based on the negative continued fractions. We combine the homological interpretation of the left and right q-deformed rational numbers and the q-deformed Farey sum, and give a homological interpretation of the q-deformed Farey sum. We also apply the above results to real quadratic irrational numbers with periodic type.
[ Reference URL ]Let q be a positive real number. The left and right q-deformed rational numbers were introduced by Bapat, Becker and Licata via regular continued fractions, and the right q-deformed rational number is exactly q-deformed rational number considered by Morier-Genoud and Ovsienko, when q is a formal parameter. They gave a homological interpretation for left and right q-deformed rational numbers by considering a special 2-Calabi–Yau category associated to the A_2 quiver.
In this talk, we begin by introducing the above definitions and related results. Then we give a formula for computing the q-deformed Farey sum of the left q-deformed rational numbers based on the negative continued fractions. We combine the homological interpretation of the left and right q-deformed rational numbers and the q-deformed Farey sum, and give a homological interpretation of the q-deformed Farey sum. We also apply the above results to real quadratic irrational numbers with periodic type.
http://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html
2023/10/10
Tuesday Seminar on Topology
17:30-18:30 Room #ハイブリッド開催/056 (Graduate School of Math. Sci. Bldg.)
Pre-registration required. See our seminar webpage.
Masato Mimura (Tohoku University)
Invariant quasimorphisms and coarse geometry of scl (JAPANESE)
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Pre-registration required. See our seminar webpage.
Masato Mimura (Tohoku University)
Invariant quasimorphisms and coarse geometry of scl (JAPANESE)
[ Abstract ]
The topic of this talk is completely independent from that of the intensive lecture (the Green--Tao theorem) from 9th to 13th, Oct. This talk is based on the series of the joint work with Morimichi Kawasaki, Mitsuaki Kimura, Takahiro Matsushita and Shuhei Maruyama. Quasimorphisms on a group are interesting objects, but for many naturally constructed groups the space of quasimorphisms tends to be either 'trivial' or infinite dimensional. We study the setting of a pair of a group and its normal subgroup, not of a single group, and invariant quasimorphisms. Then, we can obtain a non-zero finite dimensional vector space from this setting. The celebrated Bavard duality theorem is extended to this framework, and the resulting theorem yields some outcome on the coarse geometry of scl (stable commutator length). I will present an overview of the developments of this theory.
[ Reference URL ]The topic of this talk is completely independent from that of the intensive lecture (the Green--Tao theorem) from 9th to 13th, Oct. This talk is based on the series of the joint work with Morimichi Kawasaki, Mitsuaki Kimura, Takahiro Matsushita and Shuhei Maruyama. Quasimorphisms on a group are interesting objects, but for many naturally constructed groups the space of quasimorphisms tends to be either 'trivial' or infinite dimensional. We study the setting of a pair of a group and its normal subgroup, not of a single group, and invariant quasimorphisms. Then, we can obtain a non-zero finite dimensional vector space from this setting. The celebrated Bavard duality theorem is extended to this framework, and the resulting theorem yields some outcome on the coarse geometry of scl (stable commutator length). I will present an overview of the developments of this theory.
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
2023/10/05
Information Mathematics Seminar
16:50-18:35 Room #128 (Graduate School of Math. Sci. Bldg.)
Tatsuaki Okamoto (NTT)
Cryptography and Blockchain (Japanese)
Tatsuaki Okamoto (NTT)
Cryptography and Blockchain (Japanese)
[ Abstract ]
Explanation of cryptography and blockchain
Explanation of cryptography and blockchain
2023/10/03
Operator Algebra Seminars
16:45-18:15 Room #128 (Graduate School of Math. Sci. Bldg.)
Alexander Ivanov (Imperial College London)
The VOA origins of Majorana theory
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Alexander Ivanov (Imperial College London)
The VOA origins of Majorana theory
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
2023/09/25
Tokyo Probability Seminar
17:00-18:30 Room #126 (Graduate School of Math. Sci. Bldg.)
Jimmy He (MIT)
Boundary current fluctuations for the half space ASEP (English)
Jimmy He (MIT)
Boundary current fluctuations for the half space ASEP (English)
[ Abstract ]
The half space asymmetric simple exclusion process (ASEP) is an interacting particle system on the half line, with particles allowed to enter/exit at the boundary. I will discuss recent work on understanding fluctuations for the number of particles in the half space ASEP started with no particles, which exhibits the Baik-Rains phase transition between GSE, GOE, and Gaussian fluctuations as the boundary rates vary. As part of the proof, we find new distributional identities relating this system to two other models, the half space Hall-Littlewood process, and the free boundary Schur process, which allows exact formulas to be computed.
The half space asymmetric simple exclusion process (ASEP) is an interacting particle system on the half line, with particles allowed to enter/exit at the boundary. I will discuss recent work on understanding fluctuations for the number of particles in the half space ASEP started with no particles, which exhibits the Baik-Rains phase transition between GSE, GOE, and Gaussian fluctuations as the boundary rates vary. As part of the proof, we find new distributional identities relating this system to two other models, the half space Hall-Littlewood process, and the free boundary Schur process, which allows exact formulas to be computed.
2023/09/14
Applied Analysis
16:00-17:30 Room #126 (Graduate School of Math. Sci. Bldg.)
Michał Łasica (The Polish Academy of Sciences)
Bounds on the gradient of minimizers in variational denoising (English)
https://forms.gle/C39ZLdQNVHyVmJ4j8
Michał Łasica (The Polish Academy of Sciences)
Bounds on the gradient of minimizers in variational denoising (English)
[ Abstract ]
We consider minimization problem for a class of convex integral functionals composed of two terms:
-- a regularizing term of linear growth in the gradient,
-- and a fidelity term penalizing the distance from a given function.
To ensure that such functionals attain their minima, one needs to extend their domain to the BV space. In particular minimizers may exhibit jump discontinuities. I will discuss estimates on the gradient of minimizers in terms of the data, focusing on singular part of the gradient measure.
The talk is based on joint works with P. Rybka, Z. Grochulska and A. Chambolle.
[ Reference URL ]We consider minimization problem for a class of convex integral functionals composed of two terms:
-- a regularizing term of linear growth in the gradient,
-- and a fidelity term penalizing the distance from a given function.
To ensure that such functionals attain their minima, one needs to extend their domain to the BV space. In particular minimizers may exhibit jump discontinuities. I will discuss estimates on the gradient of minimizers in terms of the data, focusing on singular part of the gradient measure.
The talk is based on joint works with P. Rybka, Z. Grochulska and A. Chambolle.
https://forms.gle/C39ZLdQNVHyVmJ4j8
2023/09/07
Applied Analysis
16:00-17:30 Room #126 (Graduate School of Math. Sci. Bldg.)
Samuel Mercer (Delft University of Technology)
Uniform Convergence of Gradient Flows on a Stack of Banach Spaces (English)
https://forms.gle/T8yWr2gDTYzj8vkE7
Samuel Mercer (Delft University of Technology)
Uniform Convergence of Gradient Flows on a Stack of Banach Spaces (English)
[ Abstract ]
Within this talk I will recall the classical result: Given a sequence of convex functionals on a Hilbert space, Gamma-convergence of this sequence implies uniform convergence on finite time-intervals for their gradient flows. I will then discuss a generalisation for this result. In particular our functionals are defined on a sequence of distinct Banach spaces that can be stacked together inside of a unifying space. We will study a kind of gradient flow for our functionals inside their respective Banach space and ask the following question. What structure is necessary within our unifying space to attain uniform convergence of gradient flows?
[ Reference URL ]Within this talk I will recall the classical result: Given a sequence of convex functionals on a Hilbert space, Gamma-convergence of this sequence implies uniform convergence on finite time-intervals for their gradient flows. I will then discuss a generalisation for this result. In particular our functionals are defined on a sequence of distinct Banach spaces that can be stacked together inside of a unifying space. We will study a kind of gradient flow for our functionals inside their respective Banach space and ask the following question. What structure is necessary within our unifying space to attain uniform convergence of gradient flows?
https://forms.gle/T8yWr2gDTYzj8vkE7
2023/08/30
Discrete mathematical modelling seminar
16:30-17:30 Room #370 (Graduate School of Math. Sci. Bldg.)
Joshua Capel (University of New South Wales)
Classical structure theory for second-order semi-degenerate super-integrable systems (English)
Joshua Capel (University of New South Wales)
Classical structure theory for second-order semi-degenerate super-integrable systems (English)
[ Abstract ]
Second-order superintegrable systems have long been a subject of interest in the study of integral systems, primarily due to their close connection with separation of variables. Among these, the 'non-degenerate' second-order systems on constant curvature spaces have been particularly well studies, and are mostly understood.
A non-degenerate system in n-dimensions comprises an (n+1)-dimensional vector space of potentials, along with 2n-1 second-order constants that commute with the Hamiltonian of the system.
In contrast, a semi-degenerate system is characterised by having fewer than n+1 parameters. In this talk, we will discuss the structure theory of truly n-dimensional potentials (meaning potentials that are not just restrictions of (n+1)-dimensional counterparts). We will see that the classical structure theory appears just as rich as the non-degenerate case.
This talk is joint work with Jeremy Nugent and Jonathan Kress.
Second-order superintegrable systems have long been a subject of interest in the study of integral systems, primarily due to their close connection with separation of variables. Among these, the 'non-degenerate' second-order systems on constant curvature spaces have been particularly well studies, and are mostly understood.
A non-degenerate system in n-dimensions comprises an (n+1)-dimensional vector space of potentials, along with 2n-1 second-order constants that commute with the Hamiltonian of the system.
In contrast, a semi-degenerate system is characterised by having fewer than n+1 parameters. In this talk, we will discuss the structure theory of truly n-dimensional potentials (meaning potentials that are not just restrictions of (n+1)-dimensional counterparts). We will see that the classical structure theory appears just as rich as the non-degenerate case.
This talk is joint work with Jeremy Nugent and Jonathan Kress.
2023/08/25
thesis presentations
13:00-14:15 Room #123 (Graduate School of Math. Sci. Bldg.)
KITAMURA Kan (Graduate School of Mathematical Sciences University of Tokyo)
Discrete quantum subgroups of quantum doubles
(量子ダブルの離散部分量子群について)
KITAMURA Kan (Graduate School of Mathematical Sciences University of Tokyo)
Discrete quantum subgroups of quantum doubles
(量子ダブルの離散部分量子群について)
2023/08/24
Tokyo-Nagoya Algebra Seminar
10:30-12:00 Online
Sota Asai (University of Tokyo)
TF equivalence on the real Grothendieck group (Japanese)
[ Reference URL ]
http://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html
Sota Asai (University of Tokyo)
TF equivalence on the real Grothendieck group (Japanese)
[ Reference URL ]
http://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html
2023/08/22
Tuesday Seminar of Analysis
16:00-17:30 Room #126 (Graduate School of Math. Sci. Bldg.)
Daniel Parra (Universidad de Santiago de Chile)
Towards a Levinson's Theorem for Discrete Magnetic operators on tubes under finite rank perturbations (English)
https://forms.gle/VBp4nSnYYKVpXFhB9
Daniel Parra (Universidad de Santiago de Chile)
Towards a Levinson's Theorem for Discrete Magnetic operators on tubes under finite rank perturbations (English)
[ Abstract ]
In this talk we study a family of magnetic Hamiltonians on discrete tubes under a finite rank perturbation supported on its border. We go into detail for the case of rank $2$ and show how the eigenvalues can be related to the scattering matrix to exhibit an index theorem in the tradition of Levison’s theorem. We then turn to the general case, discuss the different spectral scenarios that can occur and explain the C*-algebraic framework that could allow us to treat this case. This is an ongoing work with S. Richard (Nagoya), V. Austen (Nagoya) and A. Rennie (Wollongong).
[ Reference URL ]In this talk we study a family of magnetic Hamiltonians on discrete tubes under a finite rank perturbation supported on its border. We go into detail for the case of rank $2$ and show how the eigenvalues can be related to the scattering matrix to exhibit an index theorem in the tradition of Levison’s theorem. We then turn to the general case, discuss the different spectral scenarios that can occur and explain the C*-algebraic framework that could allow us to treat this case. This is an ongoing work with S. Richard (Nagoya), V. Austen (Nagoya) and A. Rennie (Wollongong).
https://forms.gle/VBp4nSnYYKVpXFhB9
2023/08/21
Classical Analysis
10:00-17:30 Room #123 (Graduate School of Math. Sci. Bldg.)
Xiaomeng Xu (BICMR, China) 10:00-11:30
Stokes matrices of confluent hypergeometric systems and the isomonodromy deformation equations (ENGLISH)
Stokes matrices of quantum confluent hypergeometric systems and the representation of quantum groups (ENGLISH)
The WKB approximation of (quantum) confluent hypergeometric systems, Cauchy interlacing inequality and crystal basis (ENGLISH)
Xiaomeng Xu (BICMR, China) 10:00-11:30
Stokes matrices of confluent hypergeometric systems and the isomonodromy deformation equations (ENGLISH)
[ Abstract ]
This talk first gives an introduction to the Stokes matrices of a linear meromorphic system of Poncaré rank 1, and the associated nonlinear isomonodromy deformation equation. The nonlinear equation naturally arises from the theory of Frobenius manifolds, stability conditions, Poisson-Lie groups and so on, and can be seen as a higher rank generalizations of the sixth Painlevé equation. The talk then gives a parameterization of the asymptotics of the solutions of the isomonodromy equation at a critical point, the explicit formula of the monodromy/Stokes matrices of the linear problem via the parameterization, as well as a connection formula between two differential critical points. It can be seen as a generalization of Jimbo's work for the sixth Painlevé equation to a higher rank case. It is partially based on a joint work with Qian Tang.
Xiaomeng Xu (BICMR, China) 14:00-15:30This talk first gives an introduction to the Stokes matrices of a linear meromorphic system of Poncaré rank 1, and the associated nonlinear isomonodromy deformation equation. The nonlinear equation naturally arises from the theory of Frobenius manifolds, stability conditions, Poisson-Lie groups and so on, and can be seen as a higher rank generalizations of the sixth Painlevé equation. The talk then gives a parameterization of the asymptotics of the solutions of the isomonodromy equation at a critical point, the explicit formula of the monodromy/Stokes matrices of the linear problem via the parameterization, as well as a connection formula between two differential critical points. It can be seen as a generalization of Jimbo's work for the sixth Painlevé equation to a higher rank case. It is partially based on a joint work with Qian Tang.
Stokes matrices of quantum confluent hypergeometric systems and the representation of quantum groups (ENGLISH)
[ Abstract ]
This talk studies a quantum analog of Stokes matrices of confluent hypergeometric systems. It first gives an introduction to the Stokes phenomenon of an irregular Knizhnik–Zamolodchikov at a second order pole, associated to a regular semisimple element u and a representation $L(\lambda)$ of $gl_n$. It then shows that the Stokes matrices of the
irregular Knizhnik–Zamolodchikov equation define representation of $U_q(gl_n)$ on $L(\lambda)$. In then end, using the isomonodromy approach, it derives an explicit expression of the regularized limit of the Stokes matrices as the regular semisimple element u goes to the caterpillar point in the wonderful compactification.
Xiaomeng Xu (BICMR, China) 16:00-17:30This talk studies a quantum analog of Stokes matrices of confluent hypergeometric systems. It first gives an introduction to the Stokes phenomenon of an irregular Knizhnik–Zamolodchikov at a second order pole, associated to a regular semisimple element u and a representation $L(\lambda)$ of $gl_n$. It then shows that the Stokes matrices of the
irregular Knizhnik–Zamolodchikov equation define representation of $U_q(gl_n)$ on $L(\lambda)$. In then end, using the isomonodromy approach, it derives an explicit expression of the regularized limit of the Stokes matrices as the regular semisimple element u goes to the caterpillar point in the wonderful compactification.
The WKB approximation of (quantum) confluent hypergeometric systems, Cauchy interlacing inequality and crystal basis (ENGLISH)
[ Abstract ]
This talk studies the WKB approximation of the linear meromorphic systems of Poncaré rank 1 appearing in talk 1 and 2, via the isomonodromy approach. In the classical case, it unveils a relation between the WKB approximation, the Cauchy interlacing inequality and cluster algebras with the help of the spectral network; in the quantum case, motivated by the crystal limit of the quantum groups, it shows a relation between the WKB approximation and the gl_n-crystal structures. It is partially based on a joint work with
Anton Alekseev, Andrew Neitzke and Yan Zhou.
This talk studies the WKB approximation of the linear meromorphic systems of Poncaré rank 1 appearing in talk 1 and 2, via the isomonodromy approach. In the classical case, it unveils a relation between the WKB approximation, the Cauchy interlacing inequality and cluster algebras with the help of the spectral network; in the quantum case, motivated by the crystal limit of the quantum groups, it shows a relation between the WKB approximation and the gl_n-crystal structures. It is partially based on a joint work with
Anton Alekseev, Andrew Neitzke and Yan Zhou.
2023/08/08
Lectures
14:00-15:00 Room #123 (Graduate School of Math. Sci. Bldg.)
Dror Bar-Natan (University of Toronto)
Cars, Interchanges, Traffic Counters, and some Pretty Darned Good Knot Invariants (English)
http://www.math.toronto.edu/~drorbn/Talks/Tokyo-230808/
Dror Bar-Natan (University of Toronto)
Cars, Interchanges, Traffic Counters, and some Pretty Darned Good Knot Invariants (English)
[ Abstract ]
Reporting on joint work with Roland van der Veen, I'll tell you some stories about ρ_1, an easy to define, strong, fast to compute, homomorphic, and well-connected knot invariant. ρ_1 was first studied by Rozansky and Overbay, it is dominated by the coloured Jones polynomial (but it isn't lesser!), it has far-reaching generalizations, and I wish I understood it.
[ Reference URL ]Reporting on joint work with Roland van der Veen, I'll tell you some stories about ρ_1, an easy to define, strong, fast to compute, homomorphic, and well-connected knot invariant. ρ_1 was first studied by Rozansky and Overbay, it is dominated by the coloured Jones polynomial (but it isn't lesser!), it has far-reaching generalizations, and I wish I understood it.
http://www.math.toronto.edu/~drorbn/Talks/Tokyo-230808/
Lectures
15:30-16:30 Room #123 (Graduate School of Math. Sci. Bldg.)
Dror Bar-Natan (University of Toronto)
Shifted Partial Quadratics, their Pushwards, and Signature Invariants for Tangles (English)
http://www.math.toronto.edu/~drorbn/Talks/Tokyo-230808/
Dror Bar-Natan (University of Toronto)
Shifted Partial Quadratics, their Pushwards, and Signature Invariants for Tangles (English)
[ Abstract ]
Following a general discussion of the computation of zombians of unfinished columbaria (with examples), I will tell you about my recent joint work with Jessica Liu on what we feel is the "textbook" extension of knot signatures to tangles, which for unknown reasons, is not in any of the textbooks that we know.
[ Reference URL ]Following a general discussion of the computation of zombians of unfinished columbaria (with examples), I will tell you about my recent joint work with Jessica Liu on what we feel is the "textbook" extension of knot signatures to tangles, which for unknown reasons, is not in any of the textbooks that we know.
http://www.math.toronto.edu/~drorbn/Talks/Tokyo-230808/
2023/08/07
Tokyo Probability Seminar
17:00-18:30 Room #123 (Graduate School of Math. Sci. Bldg.)
Freddy Delbaen (Professor emeritus at ETH Zurich)
Approximation of Random Variables by Elements that are independent of a given sigma algebra (English)
Freddy Delbaen (Professor emeritus at ETH Zurich)
Approximation of Random Variables by Elements that are independent of a given sigma algebra (English)
[ Abstract ]
Given a square integrable m-dimensional random variable $X$ on a probability space $(\Omega,\mathcal{F},\mathbb{P})$ and a sub sigma algebra $\mathcal{A}$, we show that there exists another m-dimensional random variable $Y$, independent of $\mathcal{A}$ and minimising the $L^2$ distance to $X$. Such results have an importance to fairness and bias reduction in Artificial Intelligence, Machine Learning and Network Theory. The proof needs elements from transportation theory, a parametric version due to Dudley and Blackwell of the Skorohod theorem, selection theorems, … The problem also triggers other approximation problems. (joint work with C. Majumdar)
Given a square integrable m-dimensional random variable $X$ on a probability space $(\Omega,\mathcal{F},\mathbb{P})$ and a sub sigma algebra $\mathcal{A}$, we show that there exists another m-dimensional random variable $Y$, independent of $\mathcal{A}$ and minimising the $L^2$ distance to $X$. Such results have an importance to fairness and bias reduction in Artificial Intelligence, Machine Learning and Network Theory. The proof needs elements from transportation theory, a parametric version due to Dudley and Blackwell of the Skorohod theorem, selection theorems, … The problem also triggers other approximation problems. (joint work with C. Majumdar)
2023/07/31
Operator Algebra Seminars
16:45-18:15 Room #128 (Graduate School of Math. Sci. Bldg.)
Roberto Longo (Univ. Rome, ”Tor Vergata”)
Operator Algebras and Quantum Field Theory: introductory elements
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Roberto Longo (Univ. Rome, ”Tor Vergata”)
Operator Algebras and Quantum Field Theory: introductory elements
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
2023/07/28
Algebraic Geometry Seminar
13:30-15:00 Room #ハイブリッド開催/002 (Graduate School of Math. Sci. Bldg.)
Shihoko Ishii (The University of Tokyo)
TBA
Shihoko Ishii (The University of Tokyo)
TBA
2023/07/21
Algebraic Geometry Seminar
13:30-15:00 Room #ハイブリッド開催/056 (Graduate School of Math. Sci. Bldg.)
Sho Ejiri (Osaka Metropolitan University)
The Demailly--Peternell--Schneider conjecture is true in positive characteristic
Sho Ejiri (Osaka Metropolitan University)
The Demailly--Peternell--Schneider conjecture is true in positive characteristic
[ Abstract ]
In 1993, Demailly, Peternell and Schneider conjectured that the Albanese morphism of a compact K\"{a}hler manifold with nef anti-canonical divisor is surjective. For smooth projective varieties of characteristic zero, the conjecture was verified by Zhang in 1996. In positive characteristic, the conjecture was solved under the assumption that the geometric generic fiber F of the Albanese morphism has only mild singularities. However, F may have bad singularities even if we restrict ourselves to the case when the anti-canonical divisor is nef. In this talk, we prove the conjecture in positive characteristic without any extra assumption. We also discuss properties of the Albanese morphism, such as flatness or local isotriviality. This talk is based on joint work with Zsolt Patakfalvi.
In 1993, Demailly, Peternell and Schneider conjectured that the Albanese morphism of a compact K\"{a}hler manifold with nef anti-canonical divisor is surjective. For smooth projective varieties of characteristic zero, the conjecture was verified by Zhang in 1996. In positive characteristic, the conjecture was solved under the assumption that the geometric generic fiber F of the Albanese morphism has only mild singularities. However, F may have bad singularities even if we restrict ourselves to the case when the anti-canonical divisor is nef. In this talk, we prove the conjecture in positive characteristic without any extra assumption. We also discuss properties of the Albanese morphism, such as flatness or local isotriviality. This talk is based on joint work with Zsolt Patakfalvi.
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