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Seminar information archive
Seminar information archive ～04/27｜Today's seminar 04/28 | Future seminars 04/29～
2010/07/12
Seminar on Geometric Complex Analysis
10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Yu KAWAKAMI (Kyushu Univ.)
The value distribution of the Gauss map of wave fronts and its applications (JAPANESE)
Yu KAWAKAMI (Kyushu Univ.)
The value distribution of the Gauss map of wave fronts and its applications (JAPANESE)
Algebraic Geometry Seminar
16:40-18:10 Room #126 (Graduate School of Math. Sci. Bldg.)
Ryo Ohkawa (Tokyo Institute of Technology)
Flips of moduli of stable torsion free sheaves with $c_1=1$ on
$\\mathbb{P}^2$ (JAPANESE)
Ryo Ohkawa (Tokyo Institute of Technology)
Flips of moduli of stable torsion free sheaves with $c_1=1$ on
$\\mathbb{P}^2$ (JAPANESE)
[ Abstract ]
We study flips of moduli schemes of stable torsion free sheaves
on the projective plane via wall-crossing phenomena of Bridgeland stability.
They are described as stratified Grassmann bundles by variation of
stability of modules over certain finite dimensional algebra.
We study flips of moduli schemes of stable torsion free sheaves
on the projective plane via wall-crossing phenomena of Bridgeland stability.
They are described as stratified Grassmann bundles by variation of
stability of modules over certain finite dimensional algebra.
2010/07/08
Applied Analysis
16:00-17:30 Room #002 (Graduate School of Math. Sci. Bldg.)
Anna Vainchtein (University of Pittsburgh, Department of Mathematics)
Effect of nonlinearity on the steady motion of a twinning dislocation (ENGLISH)
Anna Vainchtein (University of Pittsburgh, Department of Mathematics)
Effect of nonlinearity on the steady motion of a twinning dislocation (ENGLISH)
[ Abstract ]
We consider the steady motion of a twinning dislocation in a Frenkel-Kontorova lattice with a double-well substrate potential that has a non-degenerate spinodal region. Semi-analytical traveling wave solutions are constructed for the piecewise quadratic potential, and their stability and further effects of nonlinearity are investigated numerically. We show that the width of the spinodal region and the nonlinearity of the potential have a significant effect on the dislocation kinetics, resulting in stable steady motion in some low-velocity intervals and lower propagation stress. We also conjecture that a stable steady propagation must correspond to an increasing portion of the kinetic relation between the applied stress and dislocation velocity.
We consider the steady motion of a twinning dislocation in a Frenkel-Kontorova lattice with a double-well substrate potential that has a non-degenerate spinodal region. Semi-analytical traveling wave solutions are constructed for the piecewise quadratic potential, and their stability and further effects of nonlinearity are investigated numerically. We show that the width of the spinodal region and the nonlinearity of the potential have a significant effect on the dislocation kinetics, resulting in stable steady motion in some low-velocity intervals and lower propagation stress. We also conjecture that a stable steady propagation must correspond to an increasing portion of the kinetic relation between the applied stress and dislocation velocity.
Operator Algebra Seminars
16:30-18:00 Room #122 (Graduate School of Math. Sci. Bldg.)
Dave Penneys (UC Berkeley)
Killing weeds with annular multiplicities $*10$ via quadratic tangles (ENGLISH)
Dave Penneys (UC Berkeley)
Killing weeds with annular multiplicities $*10$ via quadratic tangles (ENGLISH)
[ Abstract ]
In recent work with Morrison, Peters, and Snyder, we eliminate two
families of possible principal graphs with graph norms less than 5 using
techniques derived from Jones' work on quadratic tangles.
In recent work with Morrison, Peters, and Snyder, we eliminate two
families of possible principal graphs with graph norms less than 5 using
techniques derived from Jones' work on quadratic tangles.
2010/07/07
Seminar on Mathematics for various disciplines
10:30-11:30 Room #056 (Graduate School of Math. Sci. Bldg.)
Masahide Sato (Information Media Center, Kanazawa University)
Instabilities of steps on a vicinal face induced by the
asymmetry of diffusion field. (JAPANESE)
Masahide Sato (Information Media Center, Kanazawa University)
Instabilities of steps on a vicinal face induced by the
asymmetry of diffusion field. (JAPANESE)
GCOE Seminars
17:00-18:00 Room #002 (Graduate School of Math. Sci. Bldg.)
天野 要 (愛媛大学大学院理工学研究科)
代用電荷法による多重連結領域の数値等角写像 (JAPANESE)
http://www.infsup.jp/utnas/
天野 要 (愛媛大学大学院理工学研究科)
代用電荷法による多重連結領域の数値等角写像 (JAPANESE)
[ Abstract ]
多重連結領域の等角写像では,平行スリット領域,円弧スリット領域,放射スリット領域,円弧スリット円板領域,円弧スリット円環領域という5種の正準スリット領域が広く知られている(Nehari, 1952).遡って,Koebe(1916)はこれらを含む39種の正準スリット領域を挙げている.近年,このような多重連結領域の問題が新たに注目されている.代用電荷法を適用して,このような様々な等角写像の表現が簡潔で精度の高い近似写像関数を簡単に構成することができる.ここでは,非有界な多重連結領域から(実軸となす角を任意に指定した一般的な)直線スリット領域と,円弧放射スリット(混在)領域への場合中心に,代用電荷法による多重連結領域の数値等角写像の方法を紹介する.
[ Reference URL ]多重連結領域の等角写像では,平行スリット領域,円弧スリット領域,放射スリット領域,円弧スリット円板領域,円弧スリット円環領域という5種の正準スリット領域が広く知られている(Nehari, 1952).遡って,Koebe(1916)はこれらを含む39種の正準スリット領域を挙げている.近年,このような多重連結領域の問題が新たに注目されている.代用電荷法を適用して,このような様々な等角写像の表現が簡潔で精度の高い近似写像関数を簡単に構成することができる.ここでは,非有界な多重連結領域から(実軸となす角を任意に指定した一般的な)直線スリット領域と,円弧放射スリット(混在)領域への場合中心に,代用電荷法による多重連結領域の数値等角写像の方法を紹介する.
http://www.infsup.jp/utnas/
Numerical Analysis Seminar
17:00-18:00 Room #002 (Graduate School of Math. Sci. Bldg.)
Kaname Amano (Ehime University)
Numerical conformal mappings of multiply connected domains by the charge simulation method (JAPANESE)
[ Reference URL ]
http://www.infsup.jp/utnas/
Kaname Amano (Ehime University)
Numerical conformal mappings of multiply connected domains by the charge simulation method (JAPANESE)
[ Reference URL ]
http://www.infsup.jp/utnas/
Number Theory Seminar
16:30-17:30 Room #056 (Graduate School of Math. Sci. Bldg.)
Takahiro Tsushima (University of Tokyo)
On the stable reduction of $X_0(p^4)$ (JAPANESE)
Takahiro Tsushima (University of Tokyo)
On the stable reduction of $X_0(p^4)$ (JAPANESE)
2010/07/06
Tuesday Seminar on Topology
17:00-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)
Akira Kono (Kyoto University)
On the cohomology of free and twisted loop spaces (JAPANESE)
Akira Kono (Kyoto University)
On the cohomology of free and twisted loop spaces (JAPANESE)
[ Abstract ]
A natural extension of cohomology suspension to a free loop space is
constructed from the evaluation map and is shown to have a good
properties in cohomology calculation. This map is generalized to a
twisted loop space.
As an application, the cohomology of free and twisted loop space of
classifying spaces of compact Lie groups, including certain finite
Chevalley groups is calculated.
A natural extension of cohomology suspension to a free loop space is
constructed from the evaluation map and is shown to have a good
properties in cohomology calculation. This map is generalized to a
twisted loop space.
As an application, the cohomology of free and twisted loop space of
classifying spaces of compact Lie groups, including certain finite
Chevalley groups is calculated.
Operator Algebra Seminars
16:30-18:00 Room #118 (Graduate School of Math. Sci. Bldg.)
Robert Sims (Univ. Arizona)
On the Existence of the Dynamics for Anharmonic Quantum Oscillator Systems (ENGLISH)
Robert Sims (Univ. Arizona)
On the Existence of the Dynamics for Anharmonic Quantum Oscillator Systems (ENGLISH)
2010/07/05
Seminar on Geometric Complex Analysis
10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Shin-ichi MATSUMURA (Univ. of Tokyo)
Expression of restricted volumes with current integration (JAPANESE)
Shin-ichi MATSUMURA (Univ. of Tokyo)
Expression of restricted volumes with current integration (JAPANESE)
Algebraic Geometry Seminar
16:40-18:10 Room #126 (Graduate School of Math. Sci. Bldg.)
Katsuhisa Furukawa (Waseda University)
Rational curves on hypersurfaces (JAPANESE)
Katsuhisa Furukawa (Waseda University)
Rational curves on hypersurfaces (JAPANESE)
[ Abstract ]
Our purpose is to study the family of smooth rational curves of degree $e$ lying on a hypersurface of degree $d$ in $\\mathbb{P}^n$, and to investigate properties of this family (e.g., dimension, smoothness, connectedness).
Our starting point is the research about the family of lines (i.e., $e = 1$), which was studied by W. Barth and A. Van de Ven over $\\mathbb{C}$, and by J. Koll\\'{a}r over an algebraically closed field of arbitrary characteristic.
For the degree $e > 1$, the family of rational curves was studied by J. Harris, M. Roth, and J. Starr over $\\mathbb{C}$ in the case of $d < (n+1)/2$.
In this talk, we study the family of rational curves in arbitrary characteristic under the assumption $e = 2,3$ and $d > 1$, or $e > 3$ and $d > 2e-4$.
Our purpose is to study the family of smooth rational curves of degree $e$ lying on a hypersurface of degree $d$ in $\\mathbb{P}^n$, and to investigate properties of this family (e.g., dimension, smoothness, connectedness).
Our starting point is the research about the family of lines (i.e., $e = 1$), which was studied by W. Barth and A. Van de Ven over $\\mathbb{C}$, and by J. Koll\\'{a}r over an algebraically closed field of arbitrary characteristic.
For the degree $e > 1$, the family of rational curves was studied by J. Harris, M. Roth, and J. Starr over $\\mathbb{C}$ in the case of $d < (n+1)/2$.
In this talk, we study the family of rational curves in arbitrary characteristic under the assumption $e = 2,3$ and $d > 1$, or $e > 3$ and $d > 2e-4$.
2010/07/02
Colloquium
16:30-17:30 Room #123 (Graduate School of Math. Sci. Bldg.)
Mitsuhiro Shishikura (Kyoto University)
Hausdorff dimension and measure of conformal fractals (JAPANESE)
Mitsuhiro Shishikura (Kyoto University)
Hausdorff dimension and measure of conformal fractals (JAPANESE)
2010/06/29
Tuesday Seminar on Topology
16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)
Takahiro Kitayama (The University of Tokyo)
Non-commutative Reidemeister torsion and Morse-Novikov theory (JAPANESE)
Takahiro Kitayama (The University of Tokyo)
Non-commutative Reidemeister torsion and Morse-Novikov theory (JAPANESE)
[ Abstract ]
For a circle-valued Morse function of a closed oriented manifold, we
show that Reidemeister torsion over a non-commutative formal Laurent
polynomial ring equals the product of a certain non-commutative
Lefschetz-type zeta function and the algebraic torsion of the Novikov
complex over the ring. This gives a generalization of the results of
Hutchings-Lee and Pazhitnov on abelian coefficients. As a consequence we
obtain Morse theoretical and dynamical descriptions of the higher-order
Alexander polynomials.
For a circle-valued Morse function of a closed oriented manifold, we
show that Reidemeister torsion over a non-commutative formal Laurent
polynomial ring equals the product of a certain non-commutative
Lefschetz-type zeta function and the algebraic torsion of the Novikov
complex over the ring. This gives a generalization of the results of
Hutchings-Lee and Pazhitnov on abelian coefficients. As a consequence we
obtain Morse theoretical and dynamical descriptions of the higher-order
Alexander polynomials.
2010/06/28
Seminar on Geometric Complex Analysis
10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Kengo HIRACHI (Univ. of Tokyo)
Total Q-curvature vanishes on integrable CR manifolds (ENGLISH)
Kengo HIRACHI (Univ. of Tokyo)
Total Q-curvature vanishes on integrable CR manifolds (ENGLISH)
2010/06/26
GCOE lecture series
13:50-14:50 Room #056 (Graduate School of Math. Sci. Bldg.)
Feng Xu (UC Riverside)
On a subfactor generalization of Wall's conjecture (ENGLISH)
Feng Xu (UC Riverside)
On a subfactor generalization of Wall's conjecture (ENGLISH)
Lectures
10:00-16:10 Room #056 (Graduate School of Math. Sci. Bldg.)
Yoshimichi Ueda (Kyushu Univ.) 10:00-11:00
On the predual of non-commutative $H^\\infty$ (ENGLISH)
Hiroki Matui (Chiba Univ.) 11:20-12:20
${\\mathbf Z}^N$-actions on UHF algebras of infinite type (ENGLISH)
Feng Xu (UC Riverside) 13:50-14:50
On a subfactor generalization of Wall's conjecture (ENGLISH)
Masaki Izumi (Kyoto Univ.) 15:10-16:10
Group actions on Kirchberg algebras (ENGLISH)
Yoshimichi Ueda (Kyushu Univ.) 10:00-11:00
On the predual of non-commutative $H^\\infty$ (ENGLISH)
Hiroki Matui (Chiba Univ.) 11:20-12:20
${\\mathbf Z}^N$-actions on UHF algebras of infinite type (ENGLISH)
Feng Xu (UC Riverside) 13:50-14:50
On a subfactor generalization of Wall's conjecture (ENGLISH)
Masaki Izumi (Kyoto Univ.) 15:10-16:10
Group actions on Kirchberg algebras (ENGLISH)
2010/06/25
Classical Analysis
16:30-18:00 Room #122 (Graduate School of Math. Sci. Bldg.)
Kazuki Hiroe (University of Tokyo)
Euler transform and Weyl groups of symmetric Kac-Moody Lie algebras (JAPANESE)
Kazuki Hiroe (University of Tokyo)
Euler transform and Weyl groups of symmetric Kac-Moody Lie algebras (JAPANESE)
Lectures
15:00-17:30 Room #056 (Graduate School of Math. Sci. Bldg.)
Narutaka Ozawa (Univ. Tokyo) 15:00-16:00
Quasi-homomorphism rigidity with noncommutative targets (ENGLISH)
Yoshiko Ogata (Univ. Tokyo) 16:30-17:30
Ruelle-Lanford functions for quantum spin systems (ENGLISH)
Narutaka Ozawa (Univ. Tokyo) 15:00-16:00
Quasi-homomorphism rigidity with noncommutative targets (ENGLISH)
Yoshiko Ogata (Univ. Tokyo) 16:30-17:30
Ruelle-Lanford functions for quantum spin systems (ENGLISH)
2010/06/24
Operator Algebra Seminars
16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Thomas Sinclair (Vanderbilt Univ.)
Strong solidity of factors from lattices in SO(n,1) and SU(n,1) (ENGLISH)
Thomas Sinclair (Vanderbilt Univ.)
Strong solidity of factors from lattices in SO(n,1) and SU(n,1) (ENGLISH)
[ Abstract ]
Generalizing techniques found in Ozawa and Popa,
``On a class of II$_1$ factors with at most one Cartan subalgebra, II''
(Amer. J. Math., to appear), we show that the group factors of ICC
lattices in SO(n,1) and SU(n,1), $n\\ge2$, are strongly solid. If
time permits, we will also discuss applications to $L^2$-rigidity.
Generalizing techniques found in Ozawa and Popa,
``On a class of II$_1$ factors with at most one Cartan subalgebra, II''
(Amer. J. Math., to appear), we show that the group factors of ICC
lattices in SO(n,1) and SU(n,1), $n\\ge2$, are strongly solid. If
time permits, we will also discuss applications to $L^2$-rigidity.
Applied Analysis
16:00-17:30 Room #002 (Graduate School of Math. Sci. Bldg.)
Hideki Murakawa (University of Toyama)
Reaction-diffusion approximation to nonlinear diffusion problems (JAPANESE)
Hideki Murakawa (University of Toyama)
Reaction-diffusion approximation to nonlinear diffusion problems (JAPANESE)
GCOE Seminars
16:00-17:30 Room #002 (Graduate School of Math. Sci. Bldg.)
村川 秀樹 (富山大学大学院理工学研究部)
非線形拡散問題の反応拡散系近似 (JAPANESE)
村川 秀樹 (富山大学大学院理工学研究部)
非線形拡散問題の反応拡散系近似 (JAPANESE)
[ Abstract ]
氷の融解・水の凝固の過程を記述するステファン問題、地下水の流れを表す多孔質媒体流方程式、2種生物種の競合問題における互いの動的な干渉作用を記述する重定-川崎-寺本交差拡散系など、様々な問題を含む非線形拡散問題を取り扱う。本講演では、非線形拡散問題の解が、拡散が線形である半線形反応拡散系の解により近似されることを示す。この結果は、非線形拡散問題の解構造が、ある種の半線形反応拡散系の中に再現されることを示唆するものである。一般に、非線形問題を扱うよりも半線形問題を取り扱う方が容易であるため、本研究は非線形問題の解析や数値解析に応用できることが期待される。
氷の融解・水の凝固の過程を記述するステファン問題、地下水の流れを表す多孔質媒体流方程式、2種生物種の競合問題における互いの動的な干渉作用を記述する重定-川崎-寺本交差拡散系など、様々な問題を含む非線形拡散問題を取り扱う。本講演では、非線形拡散問題の解が、拡散が線形である半線形反応拡散系の解により近似されることを示す。この結果は、非線形拡散問題の解構造が、ある種の半線形反応拡散系の中に再現されることを示唆するものである。一般に、非線形問題を扱うよりも半線形問題を取り扱う方が容易であるため、本研究は非線形問題の解析や数値解析に応用できることが期待される。
2010/06/23
GCOE Seminars
16:30-18:00 Room #002 (Graduate School of Math. Sci. Bldg.)
村川 秀樹 (富山大学大学院理工学研究部(理学))
非線形交差拡散系の数値解法―反応拡散系近似理論の応用― (JAPANESE)
http://www.infsup.jp/utnas/
村川 秀樹 (富山大学大学院理工学研究部(理学))
非線形交差拡散系の数値解法―反応拡散系近似理論の応用― (JAPANESE)
[ Abstract ]
多成分反応拡散系において、他の成分同士、拡散が相互に依存しあっているときに、拡散が交差していると言い、そのような系は交差拡散系と呼ばれる。2種生物種の競合問題におけるお互いの動的な干渉作用を記述する重定-川崎-寺本モデルは非線形交差拡散を含む問題の代表例である。非線形交差拡散系に対する効果的な数値解法は個別の問題に対して構成され、解析されるのが現状である。現象のモデリングを行う場合など、パラメータの変更のみでなく、非線形項そのものを変えて多くの数値実験を行いたい場合がある。この様な状況に対応するために、汎用的で簡便な数値解法が望まれる。講演では、非線形交差拡散系を近似するある半線形反応拡散系を媒介することにより、そのような数値解法を導出、解析し、数値計算を通してその有用性を示す。時間が許せば、半線形反応拡散系を用いた退化放物型方程式の数値解法についても触れたい。
[ Reference URL ]多成分反応拡散系において、他の成分同士、拡散が相互に依存しあっているときに、拡散が交差していると言い、そのような系は交差拡散系と呼ばれる。2種生物種の競合問題におけるお互いの動的な干渉作用を記述する重定-川崎-寺本モデルは非線形交差拡散を含む問題の代表例である。非線形交差拡散系に対する効果的な数値解法は個別の問題に対して構成され、解析されるのが現状である。現象のモデリングを行う場合など、パラメータの変更のみでなく、非線形項そのものを変えて多くの数値実験を行いたい場合がある。この様な状況に対応するために、汎用的で簡便な数値解法が望まれる。講演では、非線形交差拡散系を近似するある半線形反応拡散系を媒介することにより、そのような数値解法を導出、解析し、数値計算を通してその有用性を示す。時間が許せば、半線形反応拡散系を用いた退化放物型方程式の数値解法についても触れたい。
http://www.infsup.jp/utnas/
Numerical Analysis Seminar
16:30-18:00 Room #002 (Graduate School of Math. Sci. Bldg.)
Hideki Murakawa (University of Toyama)
Numerical methods for nonlinear cross diffusion system: application of reaction-diffusion approximation theory (JAPANESE)
[ Reference URL ]
http://www.infsup.jp/utnas/
Hideki Murakawa (University of Toyama)
Numerical methods for nonlinear cross diffusion system: application of reaction-diffusion approximation theory (JAPANESE)
[ Reference URL ]
http://www.infsup.jp/utnas/
2010/06/22
Tuesday Seminar of Analysis
16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Ivana Alexandrova (East Carolina University)
Resonances for Magnetic Scattering by Two Solenoidal Fields at Large Separation (ENGLISH)
Ivana Alexandrova (East Carolina University)
Resonances for Magnetic Scattering by Two Solenoidal Fields at Large Separation (ENGLISH)
[ Abstract ]
We consider the problem of quantum resonances in magnetic scattering by two
solenoidal fields at large separation in two dimensions, and we study how a trajectory
oscillating between the two fields gives rise to resonances near the real axis when
the distance between two centers of fields goes to infinity. We give a sharp lower
bound on resonance widths in terms of backward amplitudes calculated explicitly for
scattering by each solenoidal field. The study is based on a new type of complex
scaling method. As an application, we also discuss the relation to semiclassical
resonances in scattering by two solenoidal fields. This is joint work with Hideo Tamura.
We consider the problem of quantum resonances in magnetic scattering by two
solenoidal fields at large separation in two dimensions, and we study how a trajectory
oscillating between the two fields gives rise to resonances near the real axis when
the distance between two centers of fields goes to infinity. We give a sharp lower
bound on resonance widths in terms of backward amplitudes calculated explicitly for
scattering by each solenoidal field. The study is based on a new type of complex
scaling method. As an application, we also discuss the relation to semiclassical
resonances in scattering by two solenoidal fields. This is joint work with Hideo Tamura.
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