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Seminar information archive
Seminar information archive ～04/18｜Today's seminar 04/19 | Future seminars 04/20～
2013/06/27
FMSP Lectures
16:30-18:00 Room #002 (Graduate School of Math. Sci. Bldg.)
Szymon M. Walczak (University of Lodz, Poland)
Geometric applications of Wasserstein distance,
Lecture (III) Curvature of metric measure spaces II
(ENGLISH)
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/~topology/Walczak.pdf
Szymon M. Walczak (University of Lodz, Poland)
Geometric applications of Wasserstein distance,
Lecture (III) Curvature of metric measure spaces II
(ENGLISH)
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/~topology/Walczak.pdf
Geometry Colloquium
10:00-11:30 Room #122 (Graduate School of Math. Sci. Bldg.)
MASAI, Hidetoshi (Tokyo Institute of Technology)
On volume formulae in terms of orthospectrum (JAPANESE)
MASAI, Hidetoshi (Tokyo Institute of Technology)
On volume formulae in terms of orthospectrum (JAPANESE)
[ Abstract ]
Bridgeman-Kahn and Calegari derived formulae to compute the volumes of compact hyperbolic n-manifolds with totally geodesic boundary in terms of orthospectrum. Here the orthospectrum is the set of length of geodesics perpendicular to the boundary at both ends. The two formulae are obtained by apparently different methods. In this talk, we prove that the two volume formulae coincide. We also discuss some interesting relationship between two formulae. This work is a joint work with Greg McShane.
Bridgeman-Kahn and Calegari derived formulae to compute the volumes of compact hyperbolic n-manifolds with totally geodesic boundary in terms of orthospectrum. Here the orthospectrum is the set of length of geodesics perpendicular to the boundary at both ends. The two formulae are obtained by apparently different methods. In this talk, we prove that the two volume formulae coincide. We also discuss some interesting relationship between two formulae. This work is a joint work with Greg McShane.
FMSP Lectures
16:00-17:30 Room #128 (Graduate School of Math. Sci. Bldg.)
Yoichiro Mori (University of Minnesota)
Mathematical model for the electrodiffusion of ions, Lecture I (JAPANESE)
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/~fmsp/files/FMSPLectures_Mori.pdf
Yoichiro Mori (University of Minnesota)
Mathematical model for the electrodiffusion of ions, Lecture I (JAPANESE)
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/~fmsp/files/FMSPLectures_Mori.pdf
2013/06/26
Number Theory Seminar
16:40-17:40 Room #056 (Graduate School of Math. Sci. Bldg.)
Kousuke Suzuki (University of Tokyo)
An explicit construction of point sets with large minimum Dick weight (JAPANESE)
Kousuke Suzuki (University of Tokyo)
An explicit construction of point sets with large minimum Dick weight (JAPANESE)
[ Abstract ]
Walsh figure of merit WAFOM($P$) is a quality measure of point sets $P$ for quasi-Monte Carlo integration constructed by a digital net method. WAFOM($P$) is bounded by the minimum Dick weight of $P^¥perp$, where the Dick weight is a generalization of Hamming weight. In this talk, we give an explicit construction of point sets with large minimum Dick weight using Niederreiter-Xing sequences and Dick's interleaving construction. These point sets are also examples of low-WAFOM point sets.
Walsh figure of merit WAFOM($P$) is a quality measure of point sets $P$ for quasi-Monte Carlo integration constructed by a digital net method. WAFOM($P$) is bounded by the minimum Dick weight of $P^¥perp$, where the Dick weight is a generalization of Hamming weight. In this talk, we give an explicit construction of point sets with large minimum Dick weight using Niederreiter-Xing sequences and Dick's interleaving construction. These point sets are also examples of low-WAFOM point sets.
2013/06/25
Tuesday Seminar on Topology
17:10-18:10 Room #056 (Graduate School of Math. Sci. Bldg.)
Tadayuki Watanabe (Shimane University)
Higher-order generalization of Fukaya's Morse homotopy
invariant of 3-manifolds (JAPANESE)
Tadayuki Watanabe (Shimane University)
Higher-order generalization of Fukaya's Morse homotopy
invariant of 3-manifolds (JAPANESE)
[ Abstract ]
In his article published in 1996, K. Fukaya constructed
a 3-manifold invariant by using Morse homotopy theory. Roughly, his
invariant is defined by considering several Morse functions on a
3-manifold and counting with weights the ways that the theta-graph can
be immersed such that edges follow gradient lines. We generalize his
construction to 3-valent graphs with arbitrary number of loops for
integral homology 3-spheres. I will also discuss extension of our method
to 3-manifolds with positive first Betti numbers.
In his article published in 1996, K. Fukaya constructed
a 3-manifold invariant by using Morse homotopy theory. Roughly, his
invariant is defined by considering several Morse functions on a
3-manifold and counting with weights the ways that the theta-graph can
be immersed such that edges follow gradient lines. We generalize his
construction to 3-valent graphs with arbitrary number of loops for
integral homology 3-spheres. I will also discuss extension of our method
to 3-manifolds with positive first Betti numbers.
Numerical Analysis Seminar
16:30-18:00 Room #002 (Graduate School of Math. Sci. Bldg.)
Teruya Minamoto (Saga University)
Digital watermarking methods using the wavelet transforms and interval arithmetic (JAPANESE)
[ Reference URL ]
http://www.infsup.jp/utnas/
Teruya Minamoto (Saga University)
Digital watermarking methods using the wavelet transforms and interval arithmetic (JAPANESE)
[ Reference URL ]
http://www.infsup.jp/utnas/
2013/06/22
Monthly Seminar on Arithmetic of Automorphic Forms
10:00-12:15 Room #123 (Graduate School of Math. Sci. Bldg.)
*** (***) 10:00-11:00
*** (JAPANESE)
*** (***) 11:15-12:15
*** (JAPANESE)
*** (***) 10:00-11:00
*** (JAPANESE)
*** (***) 11:15-12:15
*** (JAPANESE)
Monthly Seminar on Arithmetic of Automorphic Forms
10:00-12:15 Room #123 (Graduate School of Math. Sci. Bldg.)
Kei-ichi Gunji (Chiba Inst. Tech) 10:00-11:00
On the computation of the ramified Siegel series associated with
trivial character (JAPANESE)
An explicit relative trace formula for Hilbert modular forms and its applications
(JAPANESE)
Kei-ichi Gunji (Chiba Inst. Tech) 10:00-11:00
On the computation of the ramified Siegel series associated with
trivial character (JAPANESE)
[ Abstract ]
Please check the Japanese version of the web page.
Masao Tsuzuki (Sophia University) 11:15-12:15Please check the Japanese version of the web page.
An explicit relative trace formula for Hilbert modular forms and its applications
(JAPANESE)
[ Abstract ]
This is joint work with Shingo Sugiyama. In this talk, we report our recent result on relative trace formula on PGL(2) computing the spectral averages for the central L-values of quadratic base change of holomorphic Hilbert mudular forms. explicitly all local terms of the trace formula, dropping several assumptions which have always been assumed in existing works of similar theme. The following applications of our explicit relative trace formula will be explained:
(i) a spectral equidistribution result in the leve aspect for the Satake parameters weighted by central L-values;
(ii) a subconvexity bound of quadratic base change L-functions for holomorphic Hilbert cusp forms in the weight aspect;
(iii) Existence of infinitely many holomorphic Hilbert cusp forms with arbitrarily large field of definition and with non vanishing central $L$-values.
This is joint work with Shingo Sugiyama. In this talk, we report our recent result on relative trace formula on PGL(2) computing the spectral averages for the central L-values of quadratic base change of holomorphic Hilbert mudular forms. explicitly all local terms of the trace formula, dropping several assumptions which have always been assumed in existing works of similar theme. The following applications of our explicit relative trace formula will be explained:
(i) a spectral equidistribution result in the leve aspect for the Satake parameters weighted by central L-values;
(ii) a subconvexity bound of quadratic base change L-functions for holomorphic Hilbert cusp forms in the weight aspect;
(iii) Existence of infinitely many holomorphic Hilbert cusp forms with arbitrarily large field of definition and with non vanishing central $L$-values.
2013/06/20
FMSP Lectures
16:30-18:00 Room #002 (Graduate School of Math. Sci. Bldg.)
Szymon M. Walczak (University of Lodz, Poland)
Geometric applications of Wasserstein distance,
Lecture (II) Curvature of metric measure spaces I (ENGLISH)
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/~topology/Walczak.pdf
Szymon M. Walczak (University of Lodz, Poland)
Geometric applications of Wasserstein distance,
Lecture (II) Curvature of metric measure spaces I (ENGLISH)
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/~topology/Walczak.pdf
2013/06/19
Number Theory Seminar
16:40-17:40 Room #056 (Graduate School of Math. Sci. Bldg.)
Wataru Kai (University of Tokyo)
A p-adic exponential map for the Picard group and its application to curves (JAPANESE)
Wataru Kai (University of Tokyo)
A p-adic exponential map for the Picard group and its application to curves (JAPANESE)
[ Abstract ]
Let $\\mathcal{X}$ be a proper flat scheme over a complete discrete valuation ring $O_k$ of characteristic $(0,p)$. We define an exponential map from a subgroup of the first cohomology group of $O_¥mathcal{X}$ to the Picard group of $\\mathcal{X}$, mimicking the classical construction in complex geometry. This exponential map can be applied to prove a surjectivity property concerning the Albanese variety $Alb_{X}$ of a smooth variety $X$ over $k$.
Let $\\mathcal{X}$ be a proper flat scheme over a complete discrete valuation ring $O_k$ of characteristic $(0,p)$. We define an exponential map from a subgroup of the first cohomology group of $O_¥mathcal{X}$ to the Picard group of $\\mathcal{X}$, mimicking the classical construction in complex geometry. This exponential map can be applied to prove a surjectivity property concerning the Albanese variety $Alb_{X}$ of a smooth variety $X$ over $k$.
FMSP Lectures
14:40-16:10 Room #002 (Graduate School of Math. Sci. Bldg.)
Szymon M. Walczak (University of Lodz, Poland)
Geometric applications of Wasserstein distance,
Lecture (I) Wasserstein distance and optimal transportation
(ENGLISH)
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/~topology/Walczak.pdf
Szymon M. Walczak (University of Lodz, Poland)
Geometric applications of Wasserstein distance,
Lecture (I) Wasserstein distance and optimal transportation
(ENGLISH)
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/~topology/Walczak.pdf
Operator Algebra Seminars
16:30-18:00 Room #118 (Graduate School of Math. Sci. Bldg.)
Yosuke Kubota (Univ. Tokyo)
A generalization of the spectral flow and localization of index (ENGLISH)
Yosuke Kubota (Univ. Tokyo)
A generalization of the spectral flow and localization of index (ENGLISH)
2013/06/18
Tuesday Seminar on Topology
16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)
Kimihiko Motegi (Nihon University)
Left-orderable, non-L-space surgeries on knots (JAPANESE)
Kimihiko Motegi (Nihon University)
Left-orderable, non-L-space surgeries on knots (JAPANESE)
[ Abstract ]
A Dehn surgery is said to be left-orderable
if the resulting manifold of the surgery has the left-orderable fundamental group,
and a Dehn surgery is called an L-space surgery
if the resulting manifold of the surgery is an L-space.
We will focus on left-orderable, non-L-space surgeries on knots in the 3-sphere.
Once we have a knot with left-orderable surgeries,
the ``periodic construction" enables us to provide infinitely many knots with
left-orderable, non-L-space surgeries.
We apply the construction to present infinitely many hyperbolic knots on each
of which every nontrivial surgery is a left-orderable, non-L-space surgery.
This is a joint work with Masakazu Teragaito.
A Dehn surgery is said to be left-orderable
if the resulting manifold of the surgery has the left-orderable fundamental group,
and a Dehn surgery is called an L-space surgery
if the resulting manifold of the surgery is an L-space.
We will focus on left-orderable, non-L-space surgeries on knots in the 3-sphere.
Once we have a knot with left-orderable surgeries,
the ``periodic construction" enables us to provide infinitely many knots with
left-orderable, non-L-space surgeries.
We apply the construction to present infinitely many hyperbolic knots on each
of which every nontrivial surgery is a left-orderable, non-L-space surgery.
This is a joint work with Masakazu Teragaito.
Seminar on Probability and Statistics
13:00-14:10 Room #052 (Graduate School of Math. Sci. Bldg.)
MASUDA, Hiroki (Institute of Mathematics for Industry, Kyushu University)
Locally stable distribution approximation of high-frequency data (JAPANESE)
[ Reference URL ]
http://www.sigmath.es.osaka-u.ac.jp/~kamatani/statseminar/2013/01.html
MASUDA, Hiroki (Institute of Mathematics for Industry, Kyushu University)
Locally stable distribution approximation of high-frequency data (JAPANESE)
[ Reference URL ]
http://www.sigmath.es.osaka-u.ac.jp/~kamatani/statseminar/2013/01.html
2013/06/17
Seminar on Geometric Complex Analysis
10:30-12:00 Room #126 (Graduate School of Math. Sci. Bldg.)
Takato Uehara (Niigata University)
有理曲面上の自己同型写像のエントロピー (JAPANESE)
Takato Uehara (Niigata University)
有理曲面上の自己同型写像のエントロピー (JAPANESE)
2013/06/13
Lectures
16:30-18:00 Room #117 (Graduate School of Math. Sci. Bldg.)
Shinichi Mochizuki (Kyoto University, RIMS)
Introduction to inter-universal Teichmueller theory, extended version (JAPANESE)
Shinichi Mochizuki (Kyoto University, RIMS)
Introduction to inter-universal Teichmueller theory, extended version (JAPANESE)
FMSP Lectures
17:00-18:00 Room #370 (Graduate School of Math. Sci. Bldg.)
Fikret Golgeleyen (Bulent Ecevit University)
Boundary Rigidity for Riemannian Manifolds (ENGLISH)
Fikret Golgeleyen (Bulent Ecevit University)
Boundary Rigidity for Riemannian Manifolds (ENGLISH)
2013/06/12
Number Theory Seminar
17:30-18:30 Room #056 (Graduate School of Math. Sci. Bldg.)
Xinyi Yuan (University of California, Berkeley)
Hodge index theorem for adelic line bundles (ENGLISH)
Xinyi Yuan (University of California, Berkeley)
Hodge index theorem for adelic line bundles (ENGLISH)
[ Abstract ]
The Hodge index theorem of Faltings and Hriljac asserts that the Neron-Tate height pairing on a projective curve over a number field is equal to certain intersection pairing in the setting of Arakelov geometry. In the talk, I will present an extension of the result to adelic line bundles on higher dimensional varieties over finitely generated fields. Then we will talk about its relation to the non-archimedean Calabi-Yau theorem and the its application to algebraic dynamics. This is a joint work with Shou-Wu Zhang.
The Hodge index theorem of Faltings and Hriljac asserts that the Neron-Tate height pairing on a projective curve over a number field is equal to certain intersection pairing in the setting of Arakelov geometry. In the talk, I will present an extension of the result to adelic line bundles on higher dimensional varieties over finitely generated fields. Then we will talk about its relation to the non-archimedean Calabi-Yau theorem and the its application to algebraic dynamics. This is a joint work with Shou-Wu Zhang.
thesis presentations
16:30-17:45 Room #122 (Graduate School of Math. Sci. Bldg.)
Teppei OGIHARA (Center for the Study of Finance and Insurance, Osaka University)
Quasi-Likelihood Analysis for Diffusion Processes and Diffusion
Processes with Jumps (JAPANESE)
Teppei OGIHARA (Center for the Study of Finance and Insurance, Osaka University)
Quasi-Likelihood Analysis for Diffusion Processes and Diffusion
Processes with Jumps (JAPANESE)
2013/06/11
Tuesday Seminar on Topology
16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)
Takahiro Kitayama (The University of Tokyo)
On an analogue of Culler-Shalen theory for higher-dimensional
representations
(JAPANESE)
Takahiro Kitayama (The University of Tokyo)
On an analogue of Culler-Shalen theory for higher-dimensional
representations
(JAPANESE)
[ Abstract ]
Culler and Shalen established a way to construct incompressible surfaces
in a 3-manifold from ideal points of the SL_2-character variety. We
present an analogous theory to construct certain kinds of branched
surfaces from limit points of the SL_n-character variety. Such a
branched surface induces a nontrivial presentation of the fundamental
group as a 2-dimensional complex of groups. This is a joint work with
Takashi Hara (Osaka University).
Culler and Shalen established a way to construct incompressible surfaces
in a 3-manifold from ideal points of the SL_2-character variety. We
present an analogous theory to construct certain kinds of branched
surfaces from limit points of the SL_n-character variety. Such a
branched surface induces a nontrivial presentation of the fundamental
group as a 2-dimensional complex of groups. This is a joint work with
Takashi Hara (Osaka University).
Seminar on Mathematics for various disciplines
10:30-11:30 Room #056 (Graduate School of Math. Sci. Bldg.)
Ken-ichi SAWAI (Institute of Industrial Science, the University of Tokyo)
脳の同一源性推定を仮定した聴覚時間知覚のベイズモデル (JAPANESE)
Ken-ichi SAWAI (Institute of Industrial Science, the University of Tokyo)
脳の同一源性推定を仮定した聴覚時間知覚のベイズモデル (JAPANESE)
2013/06/10
Seminar on Geometric Complex Analysis
10:30-12:00 Room #126 (Graduate School of Math. Sci. Bldg.)
Shin-ichi Matsumura (Kagoshima University)
A Nadel vanishing theorem for metrics with minimal singularities on big line bundles (JAPANESE)
Shin-ichi Matsumura (Kagoshima University)
A Nadel vanishing theorem for metrics with minimal singularities on big line bundles (JAPANESE)
[ Abstract ]
In this talk, we study singular metrics with non-algebraic singularities, their multiplier ideal sheaves and a Nadel type vanishing theorem, from the view point of complex geometry. The Nadel vanishing theorem can be seen as an analytic version of the Kawamata-Viehweg vanishing theorem of algebraic geometry. The main purpose of this talk is to establish such a theorem for the multiplier ideal sheaf of a metric with minimal singularities, for the cohomology with values in a big line bundle.
In this talk, we study singular metrics with non-algebraic singularities, their multiplier ideal sheaves and a Nadel type vanishing theorem, from the view point of complex geometry. The Nadel vanishing theorem can be seen as an analytic version of the Kawamata-Viehweg vanishing theorem of algebraic geometry. The main purpose of this talk is to establish such a theorem for the multiplier ideal sheaf of a metric with minimal singularities, for the cohomology with values in a big line bundle.
2013/06/06
Geometry Colloquium
10:00-11:30 Room #122 (Graduate School of Math. Sci. Bldg.)
Hajime Fujita (Japan Women's University)
Equivariant local index and transverse index for circle action (JAPANESE)
Hajime Fujita (Japan Women's University)
Equivariant local index and transverse index for circle action (JAPANESE)
[ Abstract ]
In our joint work with Furuta and Yoshida we gave a formulation of index theory of Dirac-type operator on open Riemannian manifolds. We used a torus fibration and a perturbation by Dirac-type operator along fibers. In this talk we develop an equivariant version for circle action and apply it for Hamiltonian circle action case. We investigate the relation between our equivariant index and index of transverse elliptic operator/symbol developed by Atiyah, Paradan-Vergne and Braverman. We give a computation for the standard cylinder, which shows the difference between two equivariant indices.
In our joint work with Furuta and Yoshida we gave a formulation of index theory of Dirac-type operator on open Riemannian manifolds. We used a torus fibration and a perturbation by Dirac-type operator along fibers. In this talk we develop an equivariant version for circle action and apply it for Hamiltonian circle action case. We investigate the relation between our equivariant index and index of transverse elliptic operator/symbol developed by Atiyah, Paradan-Vergne and Braverman. We give a computation for the standard cylinder, which shows the difference between two equivariant indices.
FMSP Lectures
16:00-17:30 Room #056 (Graduate School of Math. Sci. Bldg.)
Andrei Pajitnov (Univ. de Nantes)
Real-valued and circle-valued Morse theory:
an introduction
(ENGLISH)
Andrei Pajitnov (Univ. de Nantes)
Real-valued and circle-valued Morse theory:
an introduction
(ENGLISH)
[ Abstract ]
Classical Morse theory relates the number of critical points of a Morse
function f on a manifold M to the topology of M. The main technical
ingredient of this theory is a chain complex generated by the critical points
of the function. In 1981 S.P. Novikov generalized this theory to the case of
circle-valued Morse functions. In this talk we describe the construction of
both chain complexes, based on the idea of E. Witten (1982), which allows, in
particular, to compute the boundary operators in the Morse complex from
the count of flow lines of the gradient of f. We discuss geometric applications
of these constructions.
Classical Morse theory relates the number of critical points of a Morse
function f on a manifold M to the topology of M. The main technical
ingredient of this theory is a chain complex generated by the critical points
of the function. In 1981 S.P. Novikov generalized this theory to the case of
circle-valued Morse functions. In this talk we describe the construction of
both chain complexes, based on the idea of E. Witten (1982), which allows, in
particular, to compute the boundary operators in the Morse complex from
the count of flow lines of the gradient of f. We discuss geometric applications
of these constructions.
Applied Analysis
16:00-17:30 Room #128 (Graduate School of Math. Sci. Bldg.)
Chang-Shou Lin (National Taiwan University)
The Geometry of Critical Points of Green functions On Tori (ENGLISH)
Chang-Shou Lin (National Taiwan University)
The Geometry of Critical Points of Green functions On Tori (ENGLISH)
[ Abstract ]
The Green function of a torus can be expressed by elliptic functions or Jacobic theta functions. It is not surprising the geometry of its critical points would be involved with behaviors of those classical functions. Thus, the non-degeneracy of critical points gives rise to some inequality for elliptic functions. One of consequences of our analysis is to prove any saddle point is non-degenerate, i.e., the Hessian is negative.
We will also show that the number of the critical points of Green function in any torus is either three or five critical points. Furthermore, the moduli space of tori which Green function has five critical points is a simple-connected connected set. The proof of these results use a nonlinear PDE (mean field equation) and the formula for counting zeros of modular form. For a N torsion point,the related modular form is the Eisenstein series of weight one, which was discovered by Hecke (1926). Thus, our PDE method gives a deformation of those Eisenstein series and allows us to find the zeros of those Eisenstein series.
We can generalize our results to a sum of two Green functions.
The Green function of a torus can be expressed by elliptic functions or Jacobic theta functions. It is not surprising the geometry of its critical points would be involved with behaviors of those classical functions. Thus, the non-degeneracy of critical points gives rise to some inequality for elliptic functions. One of consequences of our analysis is to prove any saddle point is non-degenerate, i.e., the Hessian is negative.
We will also show that the number of the critical points of Green function in any torus is either three or five critical points. Furthermore, the moduli space of tori which Green function has five critical points is a simple-connected connected set. The proof of these results use a nonlinear PDE (mean field equation) and the formula for counting zeros of modular form. For a N torsion point,the related modular form is the Eisenstein series of weight one, which was discovered by Hecke (1926). Thus, our PDE method gives a deformation of those Eisenstein series and allows us to find the zeros of those Eisenstein series.
We can generalize our results to a sum of two Green functions.
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