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過去の記録
過去の記録 ～07/26｜本日 07/27 | 今後の予定 07/28～
2006年09月13日(水)
関数解析セミナー
13:00-16:45 数理科学研究科棟(駒場) 123号室
Nicolas Burq氏は9月7日から13日まで、Andre Martinez氏とVania Sordoni氏は、9月11日から22日まで、東京大学数理科学研究科に滞在の予定です。
Andre' Martinez 氏 (Bologna University) 13:00-14:00
On the determination of non-analytic resonances
(joint work with T.Ramond and J. Sjostrand)
Nicolas Burq 氏 (Université de Paris Sud) 14:15-15:15
Global existence for energy critical waves in 3-d domains
(joint work with G. Lebeau and F. Planchon)
On the Born-Oppenheimer approximation of wave-operators
Nicolas Burq氏は9月7日から13日まで、Andre Martinez氏とVania Sordoni氏は、9月11日から22日まで、東京大学数理科学研究科に滞在の予定です。
Andre' Martinez 氏 (Bologna University) 13:00-14:00
On the determination of non-analytic resonances
(joint work with T.Ramond and J. Sjostrand)
Nicolas Burq 氏 (Université de Paris Sud) 14:15-15:15
Global existence for energy critical waves in 3-d domains
(joint work with G. Lebeau and F. Planchon)
[ 講演概要 ]
I will present some recent results obtained recently with G. Lebeau and F. Planchon. We prove that the energy critical (quintic) non linear wave equation in 3-d domains with Dirichlet boundary conditions is globally well posed for any initial data (with finite energy). I will give some hints about the proof of this result which is based on some recent results by Smith and Sogge on $L^p$ estimates for spectral projectors and a carefull study of the boundary value problem.
Vania Sordoni 氏 (Bologna University) 15:45-16:45I will present some recent results obtained recently with G. Lebeau and F. Planchon. We prove that the energy critical (quintic) non linear wave equation in 3-d domains with Dirichlet boundary conditions is globally well posed for any initial data (with finite energy). I will give some hints about the proof of this result which is based on some recent results by Smith and Sogge on $L^p$ estimates for spectral projectors and a carefull study of the boundary value problem.
On the Born-Oppenheimer approximation of wave-operators
2006年09月11日(月)
作用素環セミナー
16:30-18:00 数理科学研究科棟(駒場) 128号室
Claude-Alain Pillet 氏 (Univ. de Toulon et du Var)
Operator-algebraic techniques in nonequilibrium statistical mechanics
Claude-Alain Pillet 氏 (Univ. de Toulon et du Var)
Operator-algebraic techniques in nonequilibrium statistical mechanics
2006年09月06日(水)
代数学コロキウム
16:30-17:30 数理科学研究科棟(駒場) 128号室
代数幾何セミナーと共催です
Bas Edixhoven 氏 (Univ. of Leiden)
Computation of the mod l Galois representations associated to Delta
代数幾何セミナーと共催です
Bas Edixhoven 氏 (Univ. of Leiden)
Computation of the mod l Galois representations associated to Delta
2006年09月04日(月)
数理ファイナンスセミナー
17:00-18:30 数理科学研究科棟(駒場) 117号室
9月4日～6日までの3日間の日程です。講演は英語で行われます。
Freddy Delbaen 氏 (ETH)
Dynamic Risk Measures and Backward Stochastic Differential Equation
9月4日～6日までの3日間の日程です。講演は英語で行われます。
Freddy Delbaen 氏 (ETH)
Dynamic Risk Measures and Backward Stochastic Differential Equation
数理ファイナンスセミナー
15:45-16:45 数理科学研究科棟(駒場) 117号室
9月4日～6日の3日間の日程です。
楠岡成雄氏・梅澤祐二 氏 (東京大)
リスク尺度入門及び概説
9月4日～6日の3日間の日程です。
楠岡成雄氏・梅澤祐二 氏 (東京大)
リスク尺度入門及び概説
2006年08月25日(金)
代数学コロキウム
16:30-17:30 数理科学研究科棟(駒場) 128号室
いつもと曜日・部屋ともに違います
A. Marmora 氏 (パリ北大・東大/学振)
p-adic local constants
いつもと曜日・部屋ともに違います
A. Marmora 氏 (パリ北大・東大/学振)
p-adic local constants
2006年08月22日(火)
統計数学セミナー
15:30-16:40 数理科学研究科棟(駒場) 128号室
Jeannette H.C. WOERNER 氏 (University of Gottingen)
A unifying approach to inference in semimartingale and long-memory models
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2006/07.html
Jeannette H.C. WOERNER 氏 (University of Gottingen)
A unifying approach to inference in semimartingale and long-memory models
[ 講演概要 ]
Over the recent years classical stochastic volatility models based on Brownian motion have been generalized in different ways, either replacing the Brownian motion by a pure jump Levy process, which leads to a pure jump model, or by a fractional Brownian motion, which makes it possible to model both long memory or turbulent behaviour. We consider robust and easily computable estimators for the inte- grated volatility, providing insight in the level of volatility, as needed for risk measurement and pricing of variance and volatility swaps. We discuss consistency and distributional results for the power and multi- power variation estimates based on high frequency data. Furthermore, we consider robustness against additive components and compare the results for the different classes of semimartingale and fractional Brow- nian motion models.
[ 参考URL ]Over the recent years classical stochastic volatility models based on Brownian motion have been generalized in different ways, either replacing the Brownian motion by a pure jump Levy process, which leads to a pure jump model, or by a fractional Brownian motion, which makes it possible to model both long memory or turbulent behaviour. We consider robust and easily computable estimators for the inte- grated volatility, providing insight in the level of volatility, as needed for risk measurement and pricing of variance and volatility swaps. We discuss consistency and distributional results for the power and multi- power variation estimates based on high frequency data. Furthermore, we consider robustness against additive components and compare the results for the different classes of semimartingale and fractional Brow- nian motion models.
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2006/07.html
統計数学セミナー
16:50-18:00 数理科学研究科棟(駒場) 128号室
Delphine DAVID 氏 (Departement de Mathematiques, Universite de La Rochelle)
A computation of Theta in a jump diffusion model by integration by parts
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2006/08.html
Delphine DAVID 氏 (Departement de Mathematiques, Universite de La Rochelle)
A computation of Theta in a jump diffusion model by integration by parts
[ 講演概要 ]
Using Malliavin weights in a jump-diffusion model we obtain an expression for Theta (the sensitivity of an option price with respect to the time remaining until exercise), with application to non-smooth payoff functions. Optimal weights are computed by minimization of variance and numerical simulations are presented for digital and European options. Some results are also presented for Asian options. Our representation formula for Theta differs in general from the one obtained from the Black-Scholes PDE in terms of Delta and Gamma.
[ 参考URL ]Using Malliavin weights in a jump-diffusion model we obtain an expression for Theta (the sensitivity of an option price with respect to the time remaining until exercise), with application to non-smooth payoff functions. Optimal weights are computed by minimization of variance and numerical simulations are presented for digital and European options. Some results are also presented for Asian options. Our representation formula for Theta differs in general from the one obtained from the Black-Scholes PDE in terms of Delta and Gamma.
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2006/08.html
2006年08月03日(木)
作用素環セミナー
16:30-18:00 数理科学研究科棟(駒場) 128号室
George Elliott 氏 (University of Toronto)
The Cuntz semigroup as an invariant for $C^*$-algebras
George Elliott 氏 (University of Toronto)
The Cuntz semigroup as an invariant for $C^*$-algebras
2006年07月31日(月)
Lie群論・表現論セミナー
15:00-17:30 数理科学研究科棟(駒場) 126号室
Guster Olafsson 氏 (Louisiana State University) 15:00-16:00
The Heat equation, the Segal-Bargmann transform and generalizations - II
[ 参考URL ]
http://akagi.ms.u-tokyo.ac.jp/seminar.html
Boris Rubin 氏 (Louisiana State University) 16:30-17:30
Radon transforms on Grassmannians and Matrix Spaces
http://akagi.ms.u-tokyo.ac.jp/seminar.html
Guster Olafsson 氏 (Louisiana State University) 15:00-16:00
The Heat equation, the Segal-Bargmann transform and generalizations - II
[ 参考URL ]
http://akagi.ms.u-tokyo.ac.jp/seminar.html
Boris Rubin 氏 (Louisiana State University) 16:30-17:30
Radon transforms on Grassmannians and Matrix Spaces
[ 講演概要 ]
Diverse geometric problems in $R^N$ get a new flavor if a generic point $x=(x_1,...,x_N)$ is regarded as a matrix with appropriately organized entries (set, e.g., $x=(x_{i,j})_{n \\times m}$ for $N=nm$). This well known observation has led to a series of breakthrough achievements in mathematics. In integral geometry it suggests a number of the so-called ``higher-rank" problems when such traditional scalar notions as ``distance", ``angle", and ``scaling" become matrix-valued. I will be speaking about Radon transforms on Grassmann manifolds and matrix spaces and some related problems of harmonic analysis where these phenomena come into play.
[ 参考URL ]Diverse geometric problems in $R^N$ get a new flavor if a generic point $x=(x_1,...,x_N)$ is regarded as a matrix with appropriately organized entries (set, e.g., $x=(x_{i,j})_{n \\times m}$ for $N=nm$). This well known observation has led to a series of breakthrough achievements in mathematics. In integral geometry it suggests a number of the so-called ``higher-rank" problems when such traditional scalar notions as ``distance", ``angle", and ``scaling" become matrix-valued. I will be speaking about Radon transforms on Grassmann manifolds and matrix spaces and some related problems of harmonic analysis where these phenomena come into play.
http://akagi.ms.u-tokyo.ac.jp/seminar.html
2006年07月25日(火)
Lie群論・表現論セミナー
16:30-18:00 数理科学研究科棟(駒場) 126号室
Boris Rubin 氏 (Louisiana State University)
Radon Transforms: Basic Concepts
http://akagi.ms.u-tokyo.ac.jp/seminar.html
Boris Rubin 氏 (Louisiana State University)
Radon Transforms: Basic Concepts
[ 講演概要 ]
How can we reconstruct a function on a manifold from integrals of this function over certain submanifolds?
This is one of the central problems in integral geometry and tomography, which leads to the notion of the Radon transform.
The first talk is of introductory character.
We discuss basic ideas of the original Radon's paper (1917), then proceed to the Minkowski-Funk transform and more general totally geodesic Radon transforms on the $n$-dimensional unit sphere.
The main emphasis is an intimate connection of these transforms with the relevant harmonic analysis.
We will see that Radon transforms of this type and their inverses can be regarded as members of analytic families of suitable convolution operators and successfully studied in the framework of these families.
I also plan to discuss an open problem of small divisors on the unit sphere, which arises in studying injectivity of generalized Minkowski-Funk transforms for non-central spherical sections.
[ 参考URL ]How can we reconstruct a function on a manifold from integrals of this function over certain submanifolds?
This is one of the central problems in integral geometry and tomography, which leads to the notion of the Radon transform.
The first talk is of introductory character.
We discuss basic ideas of the original Radon's paper (1917), then proceed to the Minkowski-Funk transform and more general totally geodesic Radon transforms on the $n$-dimensional unit sphere.
The main emphasis is an intimate connection of these transforms with the relevant harmonic analysis.
We will see that Radon transforms of this type and their inverses can be regarded as members of analytic families of suitable convolution operators and successfully studied in the framework of these families.
I also plan to discuss an open problem of small divisors on the unit sphere, which arises in studying injectivity of generalized Minkowski-Funk transforms for non-central spherical sections.
http://akagi.ms.u-tokyo.ac.jp/seminar.html
2006年07月24日(月)
トポロジー火曜セミナー
16:30-17:30 数理科学研究科棟(駒場) 056号室
曜日が異なります。ご注意下さい。
Boris Hasselblatt 氏 (Tufts University)
Invariant foliations in hyperbolic dynamics:
Smoothness and smooth equivalence
http://faculty.ms.u-tokyo.ac.jp/~topology/
曜日が異なります。ご注意下さい。
Boris Hasselblatt 氏 (Tufts University)
Invariant foliations in hyperbolic dynamics:
Smoothness and smooth equivalence
[ 講演概要 ]
The stable and unstable leaves of a hyperbolic dynamical system are smooth and form a continuous foliation. Smoothness of this foliation sometimes constrains the topological type of the foliation, other times restricts at least the smooth equivalence class of the dynamical system, or for geodesic flows, the type of the underlying manifold. I will present a broad introduction as well as recent work, work in progress, and open problems.
[ 参考URL ]The stable and unstable leaves of a hyperbolic dynamical system are smooth and form a continuous foliation. Smoothness of this foliation sometimes constrains the topological type of the foliation, other times restricts at least the smooth equivalence class of the dynamical system, or for geodesic flows, the type of the underlying manifold. I will present a broad introduction as well as recent work, work in progress, and open problems.
http://faculty.ms.u-tokyo.ac.jp/~topology/
2006年07月20日(木)
作用素環セミナー
16:30-18:00 数理科学研究科棟(駒場) 052号室
緒方芳子 氏 (東大数理・学振)
Linear response theory in quantum statistical mechanics
緒方芳子 氏 (東大数理・学振)
Linear response theory in quantum statistical mechanics
Lie群論・表現論セミナー
16:30-18:00 数理科学研究科棟(駒場) 126号室
Guster Olafsson 氏 (Louisiana State University)
The Heat equation, the Segal-Bargmann transform and generalizations - I
[ 参考URL ]
http://akagi.ms.u-tokyo.ac.jp/seminar.html
Guster Olafsson 氏 (Louisiana State University)
The Heat equation, the Segal-Bargmann transform and generalizations - I
[ 参考URL ]
http://akagi.ms.u-tokyo.ac.jp/seminar.html
2006年07月19日(水)
統計数学セミナー
16:20-17:30 数理科学研究科棟(駒場) 128号室
深澤 正彰 氏 (東京大学大学院数理科学研究科)
Edgeworth Expansion for Likelihood Analysis on Ergodic Diffusions with applications to Bootstrap
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2006/06.html
深澤 正彰 氏 (東京大学大学院数理科学研究科)
Edgeworth Expansion for Likelihood Analysis on Ergodic Diffusions with applications to Bootstrap
[ 講演概要 ]
We shall consider the maximal lilelihood estimator for the drift coefficient of a given one-dimensional diffusion. An Edgeworth expansion formula will be presented and verify a second-order correct confidence interval we shall newly propose. We are also going to mention the likelihood ratio statistic, which enjoys second-order correctness. There are Bootstrap methods closely related to the subject and introduced recently by the author. Some generalized results on those methods will be also introduced in this talk.
[ 参考URL ]We shall consider the maximal lilelihood estimator for the drift coefficient of a given one-dimensional diffusion. An Edgeworth expansion formula will be presented and verify a second-order correct confidence interval we shall newly propose. We are also going to mention the likelihood ratio statistic, which enjoys second-order correctness. There are Bootstrap methods closely related to the subject and introduced recently by the author. Some generalized results on those methods will be also introduced in this talk.
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2006/06.html
2006年07月13日(木)
作用素環セミナー
16:30-18:00 数理科学研究科棟(駒場) 052号室
小沢登高 氏 (東大数理)
Property (T) for universal lattices, after Y. Shalom
小沢登高 氏 (東大数理)
Property (T) for universal lattices, after Y. Shalom
[ 講演概要 ]
I will talk on Shalom's recent result that
$SL_n(Z[X])$ ($n\\geq 3$) has the property (T).
The talk should be elementary.
I will talk on Shalom's recent result that
$SL_n(Z[X])$ ($n\\geq 3$) has the property (T).
The talk should be elementary.
2006年07月12日(水)
代数学コロキウム
16:30-17:30 数理科学研究科棟(駒場) 117号室
桜井 真 氏 (東京大学理学系研究科)
Beilinson-Drinfeld chiral algebra, geometric Langlands program and open Gromov-Witten invariants
桜井 真 氏 (東京大学理学系研究科)
Beilinson-Drinfeld chiral algebra, geometric Langlands program and open Gromov-Witten invariants
[ 講演概要 ]
都合により、とりやめになりました。
都合により、とりやめになりました。
数理ファイナンスセミナー
18:30-20:00 数理科学研究科棟(駒場) 118号室
高岡 浩一郎 氏 (一橋大)
A complete-market generalization of the Black-Scholes model
高岡 浩一郎 氏 (一橋大)
A complete-market generalization of the Black-Scholes model
PDE実解析研究会
10:30-11:30 数理科学研究科棟(駒場) 056号室
Piotr Rybka 氏 (Warsaw University)
Analysis of a crystal growth model
http://coe.math.sci.hokudai.ac.jp/sympo/pde_ra/index.html
Piotr Rybka 氏 (Warsaw University)
Analysis of a crystal growth model
[ 講演概要 ]
We are concerned with mathematical model of a single crystal growing from vapor. Mathematically this is an exterior, one-phase Stefan-type problem with Gibbs-Thomson law. We restrict our attention to an idealization of a ice crystal, i.e. our evolving free boundary is a circular cylinder. The system under consideration consists of an equation for the motion of the free boundary (the crystal surface) coupled to the quasi-steady approximation of the diffusion equation for the supersaturation of vapor. We present analysis of the system, we show well-posedness and draw the phase portrait, we use here the fact that we need just to variable to describe evolution of a cylinder.
We are mostly concerned with the shape-persitency problem of the
evolution. The problem is, the Gibbs-Thomson relation is in fact a
driven, weighted, mean, singular curvature flow and it is not obvious that the shape of the initial interface will persists throughout the evolution or even for some time. In order to solve this problem we show existence of the region in the phase plane which is a neighborhood of a unique steady state, such that in this region the shape of the cylinder is preserved. However, this set is not invariant with respect to dynamics of the problem.
It is a very interesting question what happens to surface of our crystal at the boundary of the shape-persitency (or shape stability) region. This problem in its full generality is open. However, we give some insight by studying the Gibbs-Thomson relation with a given driving, which inherits properties of the coupling to the diffusion field. We study the resulting driven weighted mean curvature flow for graphs and some special closed Lipschitz curves. We show well-posedness of the problem, but mainly we exhibit the phenomenon of bending flat parts of the curve, which grow ``too big''.
[ 参考URL ]We are concerned with mathematical model of a single crystal growing from vapor. Mathematically this is an exterior, one-phase Stefan-type problem with Gibbs-Thomson law. We restrict our attention to an idealization of a ice crystal, i.e. our evolving free boundary is a circular cylinder. The system under consideration consists of an equation for the motion of the free boundary (the crystal surface) coupled to the quasi-steady approximation of the diffusion equation for the supersaturation of vapor. We present analysis of the system, we show well-posedness and draw the phase portrait, we use here the fact that we need just to variable to describe evolution of a cylinder.
We are mostly concerned with the shape-persitency problem of the
evolution. The problem is, the Gibbs-Thomson relation is in fact a
driven, weighted, mean, singular curvature flow and it is not obvious that the shape of the initial interface will persists throughout the evolution or even for some time. In order to solve this problem we show existence of the region in the phase plane which is a neighborhood of a unique steady state, such that in this region the shape of the cylinder is preserved. However, this set is not invariant with respect to dynamics of the problem.
It is a very interesting question what happens to surface of our crystal at the boundary of the shape-persitency (or shape stability) region. This problem in its full generality is open. However, we give some insight by studying the Gibbs-Thomson relation with a given driving, which inherits properties of the coupling to the diffusion field. We study the resulting driven weighted mean curvature flow for graphs and some special closed Lipschitz curves. We show well-posedness of the problem, but mainly we exhibit the phenomenon of bending flat parts of the curve, which grow ``too big''.
http://coe.math.sci.hokudai.ac.jp/sympo/pde_ra/index.html
2006年07月11日(火)
トポロジー火曜セミナー
17:00-18:30 数理科学研究科棟(駒場) 056号室
野田健夫 氏 (秋田大学工学資源学部)
全葉層の存在について(浅岡正幸,Emmanuel Dufraineとの共同研究)
http://faculty.ms.u-tokyo.ac.jp/~topology/
野田健夫 氏 (秋田大学工学資源学部)
全葉層の存在について(浅岡正幸,Emmanuel Dufraineとの共同研究)
[ 講演概要 ]
n次元多様体上のn個の余次元1葉層構造の組で、n個の葉層構造の接空間の共通部分が各点で0になるものを全葉層と呼ぶ。3次元の場合においては任意の有向閉多様体上に全葉層が存在することが Hardorpによって示されていた。3次元多様体上の全葉層をなす各々の葉層構造の接平面場は互いにホモトピックでありオイラー類が0になることが容易に分かるが、逆にオイラー類が0の平面場を与えたときそれを実現する全葉層が存在するかという問題が自然に生じる。
本講演ではこの問題に肯定的な解決をあたえる。
また、この結果の応用として双接触構造、すなわち横断的に交わる正と負の接触構造の組の存在問題にも触れたい。
[ 参考URL ]n次元多様体上のn個の余次元1葉層構造の組で、n個の葉層構造の接空間の共通部分が各点で0になるものを全葉層と呼ぶ。3次元の場合においては任意の有向閉多様体上に全葉層が存在することが Hardorpによって示されていた。3次元多様体上の全葉層をなす各々の葉層構造の接平面場は互いにホモトピックでありオイラー類が0になることが容易に分かるが、逆にオイラー類が0の平面場を与えたときそれを実現する全葉層が存在するかという問題が自然に生じる。
本講演ではこの問題に肯定的な解決をあたえる。
また、この結果の応用として双接触構造、すなわち横断的に交わる正と負の接触構造の組の存在問題にも触れたい。
http://faculty.ms.u-tokyo.ac.jp/~topology/
Lie群論・表現論セミナー
16:30-18:00 数理科学研究科棟(駒場) 126号室
縫田 光司 氏 (産業技術総合研究所)
On the isomorphism problem of Coxeter groups and related topics
http://akagi.ms.u-tokyo.ac.jp/seminar.html
縫田 光司 氏 (産業技術総合研究所)
On the isomorphism problem of Coxeter groups and related topics
[ 講演概要 ]
コクセター群について、そのコクセター系としての同型類がコクセターグラフと一対一対応することは周知の事実であるが、一方で抽象群としての同型類は(ワイル群の場合に限っても)そのような対応をしていない。今回は、この同型類の決定問題について、その歴史のあらまし(特に、無限群も含めた一般の場合について、10年ほど前まで殆ど何の結果も得られていなかったことは特筆に価する)と、近年の研究の進展状況を、具体例や関連する結果を交えつつ紹介する。
[ 参考URL ]コクセター群について、そのコクセター系としての同型類がコクセターグラフと一対一対応することは周知の事実であるが、一方で抽象群としての同型類は(ワイル群の場合に限っても)そのような対応をしていない。今回は、この同型類の決定問題について、その歴史のあらまし(特に、無限群も含めた一般の場合について、10年ほど前まで殆ど何の結果も得られていなかったことは特筆に価する)と、近年の研究の進展状況を、具体例や関連する結果を交えつつ紹介する。
http://akagi.ms.u-tokyo.ac.jp/seminar.html
2006年07月10日(月)
複素解析幾何セミナー
10:30-12:00 数理科学研究科棟(駒場) 128号室
Do Duc Thai 氏 (Hanoi教育大)
Characterization of domains in $C^n$ by their noncompact automorphism groups
Do Duc Thai 氏 (Hanoi教育大)
Characterization of domains in $C^n$ by their noncompact automorphism groups
[ 講演概要 ]
In this talk, the characterization of domains in $C^n$ by their noncompact automorphism groups are given. By this characterization, the Bedford-Pinchuk theorem is true for any domain (not necessary bounded) in $C^n$.
In this talk, the characterization of domains in $C^n$ by their noncompact automorphism groups are given. By this characterization, the Bedford-Pinchuk theorem is true for any domain (not necessary bounded) in $C^n$.
2006年07月08日(土)
保型形式の整数論月例セミナー
13:30-15:45 数理科学研究科棟(駒場) 123号室
伴 克馬 氏 (東京大学大学院数理科学研究科) 13:30-14:30
Rankin-Cohen-Ibukiyama operators for holomorphic automorphic forms on type I symmetric domains
谷口 隆 氏 (東京大学大学院数理科学研究科) 14:45-15:45
On Dirichlet series counting cubic alegebras
伴 克馬 氏 (東京大学大学院数理科学研究科) 13:30-14:30
Rankin-Cohen-Ibukiyama operators for holomorphic automorphic forms on type I symmetric domains
谷口 隆 氏 (東京大学大学院数理科学研究科) 14:45-15:45
On Dirichlet series counting cubic alegebras
2006年07月07日(金)
談話会・数理科学講演会
16:30-17:30 数理科学研究科棟(駒場) 123号室
お茶&Coffee&お菓子: 16:00～16:30(コモンルーム)
重定 南奈子 氏 (同志社大学)
周期的変動環境下における侵入生物の時空間パターンと伝播速度
お茶&Coffee&お菓子: 16:00～16:30(コモンルーム)
重定 南奈子 氏 (同志社大学)
周期的変動環境下における侵入生物の時空間パターンと伝播速度
[ 講演概要 ]
侵入生物の空間的な伝播に関する数理的研究は,Fisher (1937)の先駆的研究以来,外来植物や昆虫,伝染病などの侵入を中心に,主として一様な空間における拡散増殖モデルを用いて進められてきた.しかし,実際の自然環境は,森,林,河川,道路などの,生物にとって好適な環境と不適な環境がパッチ状に入り混じっており,決して一様な空間とはいえない.
本研究では、帯状の好適生息地と不適な生息地が交互に配列する2次元縞状 分断環境の中を、侵入生物が分布拡大する過程を拡散係数と増殖率が好適生息 地と不適生息地で異なる拡張Fisher modelを用いて記述し、それを heuristicな方法を用いて解くことにより,侵入種の分布拡大パターン,ならびに,伝播速度の数学公式を導いた.
侵入生物の空間的な伝播に関する数理的研究は,Fisher (1937)の先駆的研究以来,外来植物や昆虫,伝染病などの侵入を中心に,主として一様な空間における拡散増殖モデルを用いて進められてきた.しかし,実際の自然環境は,森,林,河川,道路などの,生物にとって好適な環境と不適な環境がパッチ状に入り混じっており,決して一様な空間とはいえない.
本研究では、帯状の好適生息地と不適な生息地が交互に配列する2次元縞状 分断環境の中を、侵入生物が分布拡大する過程を拡散係数と増殖率が好適生息 地と不適生息地で異なる拡張Fisher modelを用いて記述し、それを heuristicな方法を用いて解くことにより,侵入種の分布拡大パターン,ならびに,伝播速度の数学公式を導いた.
2006年07月06日(木)
アジア数学史セミナー
17:00-18:30 数理科学研究科棟(駒場) 123号室
斎藤 憲 氏 (大阪府立大学 人間社会学部)
ユークリッドをめぐる最新の研究動向
[ 参考URL ]
https://www.ms.u-tokyo.ac.jp/~kawazumi/asia.html
斎藤 憲 氏 (大阪府立大学 人間社会学部)
ユークリッドをめぐる最新の研究動向
[ 参考URL ]
https://www.ms.u-tokyo.ac.jp/~kawazumi/asia.html
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