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解析学火曜セミナー
過去の記録 ～05/01｜次回の予定｜今後の予定 05/02～
| 開催情報 | 火曜日 16:00～17:30 数理科学研究科棟(駒場) 156号室 |
|---|---|
| 担当者 | 石毛 和弘, 坂井 秀隆, 伊藤 健一 |
| セミナーURL | https://www.ms.u-tokyo.ac.jp/seminar/analysis/ |
過去の記録
2014年04月22日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
筒井 容平 氏 (東大 数理)
拡散性を有しない誘因因子に対する走化性方程式の小さな有界な解 (JAPANESE)
筒井 容平 氏 (東大 数理)
拡散性を有しない誘因因子に対する走化性方程式の小さな有界な解 (JAPANESE)
[ 講演概要 ]
We consider a chemotaxis system with a logarithmic
sensitivity and a non-diffusive chemical substance. For some chemotactic
sensitivity constants, Ahn and Kang proved the existence of bounded
global solutions to the system. An entropy functional was used in their
argument to control the cell density by the density of the chemical
substance. Our purpose is to show the existence of bounded global
solutions for all the chemotactic sensitivity constants. Assuming the
smallness on the initial data in some sense, we can get uniform
estimates for time. These estimates are used to extend local solutions.
This talk is partially based on joint work with Yoshie Sugiyama (Kyusyu
Univ.) and Juan J. L. Vel\\'azquez (Univ. of Bonn).
We consider a chemotaxis system with a logarithmic
sensitivity and a non-diffusive chemical substance. For some chemotactic
sensitivity constants, Ahn and Kang proved the existence of bounded
global solutions to the system. An entropy functional was used in their
argument to control the cell density by the density of the chemical
substance. Our purpose is to show the existence of bounded global
solutions for all the chemotactic sensitivity constants. Assuming the
smallness on the initial data in some sense, we can get uniform
estimates for time. These estimates are used to extend local solutions.
This talk is partially based on joint work with Yoshie Sugiyama (Kyusyu
Univ.) and Juan J. L. Vel\\'azquez (Univ. of Bonn).
2014年01月28日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
This seminar is cosponsored by the GCOE program.
Arnaud Ducrot 氏 (ボルドー大学)
Asymptotic behaviour of a non-local diffusive logistic equation (ENGLISH)
This seminar is cosponsored by the GCOE program.
Arnaud Ducrot 氏 (ボルドー大学)
Asymptotic behaviour of a non-local diffusive logistic equation (ENGLISH)
[ 講演概要 ]
In this talk we investigate the long time behaviour of a logistic type equation modelling the motion of cells. The equation we consider takes into account birth and death process using a simple logistic effect as well as a non-local motion of cells using non-local Darcy’s law with regular kernel. Using the periodic framework we first investigate the well-posedness of the problem before deriving some information about its long time behaviour. The lack of asymptotic compactness of the system is overcome by making use of Young measure theory. This allows us to conclude that the semiflow converges for the Young measure topology.
In this talk we investigate the long time behaviour of a logistic type equation modelling the motion of cells. The equation we consider takes into account birth and death process using a simple logistic effect as well as a non-local motion of cells using non-local Darcy’s law with regular kernel. Using the periodic framework we first investigate the well-posedness of the problem before deriving some information about its long time behaviour. The lack of asymptotic compactness of the system is overcome by making use of Young measure theory. This allows us to conclude that the semiflow converges for the Young measure topology.
2014年01月21日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
浜向 直 氏 (東大数理)
符号付き距離関数との比較に基づく改良された等高面法 (JAPANESE)
浜向 直 氏 (東大数理)
符号付き距離関数との比較に基づく改良された等高面法 (JAPANESE)
[ 講演概要 ]
等高面法では、各時刻における曲面をある補助関数のゼロ等高面として表示し、
その補助関数に対する偏微分方程式を解くことで曲面の動きを求める。 しかし
時間が経つにつれて解の傾きが小さくなることがあり、 計算機では等高面を取
り出すことが困難となる。 そこで本講演では、方程式を適当に修正すること
で、 ゼロ等高面付近で傾きが小さくならない解が得られることを、 符号付き距
離関数との比較を通して示す。
等高面法では、各時刻における曲面をある補助関数のゼロ等高面として表示し、
その補助関数に対する偏微分方程式を解くことで曲面の動きを求める。 しかし
時間が経つにつれて解の傾きが小さくなることがあり、 計算機では等高面を取
り出すことが困難となる。 そこで本講演では、方程式を適当に修正すること
で、 ゼロ等高面付近で傾きが小さくならない解が得られることを、 符号付き距
離関数との比較を通して示す。
2014年01月14日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
伊藤 健一 氏 (筑波大)
Threshold properties for one-dimensional discrete Schr\\"odinger operators (JAPANESE)
伊藤 健一 氏 (筑波大)
Threshold properties for one-dimensional discrete Schr\\"odinger operators (JAPANESE)
[ 講演概要 ]
We study the relation between the generalized eigenspace and the asymptotic expansion of the resolvent around the threshold $0$ for the one-dimensional discrete Schr\\"odinger operator on $\\mathbb Z$. We decompose the generalized eigenspace into the subspaces corresponding to the eigenstates and the resonance states only by their asymptotics at infinity, and classify the coefficient operators of the singlar part of resolvent expansion completely in terms of these eigenspaces. Here the generalized eigenspace we consider is largest possible. For an explicit computation of the resolvent expansion we apply the expansion scheme of Jensen-Nenciu (2001). This talk is based on the recent joint work with Arne Jensen (Aalborg University).
We study the relation between the generalized eigenspace and the asymptotic expansion of the resolvent around the threshold $0$ for the one-dimensional discrete Schr\\"odinger operator on $\\mathbb Z$. We decompose the generalized eigenspace into the subspaces corresponding to the eigenstates and the resonance states only by their asymptotics at infinity, and classify the coefficient operators of the singlar part of resolvent expansion completely in terms of these eigenspaces. Here the generalized eigenspace we consider is largest possible. For an explicit computation of the resolvent expansion we apply the expansion scheme of Jensen-Nenciu (2001). This talk is based on the recent joint work with Arne Jensen (Aalborg University).
2013年12月17日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
Fabricio Macia 氏 (Universidad Politécnica de Madrid)
Dispersion and observability for completely integrable Schrödinger flows (ENGLISH)
Fabricio Macia 氏 (Universidad Politécnica de Madrid)
Dispersion and observability for completely integrable Schrödinger flows (ENGLISH)
[ 講演概要 ]
I will present some results on weak dispersion and unique continuation (observability) for linear Schrödinger
equations that are obtained as the quantization of a completely integrable Hamiltonian system.
The model case corresponds to the linear Schrödinger equation (with a potential) on the flat torus.
Our results are obtained through a detailed analysis of semiclassical measures corresponding to
sequences of solutions, which is performed using a two-microlocal approach.
This is a joint work with Nalini Anantharaman and Clotilde Fermanian-Kammerer.
I will present some results on weak dispersion and unique continuation (observability) for linear Schrödinger
equations that are obtained as the quantization of a completely integrable Hamiltonian system.
The model case corresponds to the linear Schrödinger equation (with a potential) on the flat torus.
Our results are obtained through a detailed analysis of semiclassical measures corresponding to
sequences of solutions, which is performed using a two-microlocal approach.
This is a joint work with Nalini Anantharaman and Clotilde Fermanian-Kammerer.
2013年12月10日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
Abel Klein 氏 (UC Irvine)
Quantitative unique continuation principle, local behavior of solutions, and bounds on the density of states for Schr\\"odinger operators (ENGLISH)
Abel Klein 氏 (UC Irvine)
Quantitative unique continuation principle, local behavior of solutions, and bounds on the density of states for Schr\\"odinger operators (ENGLISH)
[ 講演概要 ]
We establish bounds on the density of states measure for Schr\\"odinger operators. These are deterministic results that do not require the existence of the density of states measure, or, equivalently, of the integrated density of states. The results are stated in terms of a ``density of states outer-measure'' that always exists, and provides an upper bound for the density of states measure when it exists. We prove log-H\\"older continuity for this density of states outer-measure in one, two, and three dimensions for Schr\\"odinger operators, and in any dimension for discrete Schr\\"odinger operators. Our proofs use a quantitative unique continuation principle and the local behavior of approximate solutions of the stationary Schr\\"odinger equation.
(Joint work with Jean Bourgain.)
References: Jean Bourgain and Abel Klein: Bounds on the density of states for Schr\\"odinger operators. Invent. Math. 194, 41-72 (2013).
We establish bounds on the density of states measure for Schr\\"odinger operators. These are deterministic results that do not require the existence of the density of states measure, or, equivalently, of the integrated density of states. The results are stated in terms of a ``density of states outer-measure'' that always exists, and provides an upper bound for the density of states measure when it exists. We prove log-H\\"older continuity for this density of states outer-measure in one, two, and three dimensions for Schr\\"odinger operators, and in any dimension for discrete Schr\\"odinger operators. Our proofs use a quantitative unique continuation principle and the local behavior of approximate solutions of the stationary Schr\\"odinger equation.
(Joint work with Jean Bourgain.)
References: Jean Bourgain and Abel Klein: Bounds on the density of states for Schr\\"odinger operators. Invent. Math. 194, 41-72 (2013).
2013年11月26日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
水谷 治哉 氏 (学習院大学)
Global Strichartz estimates for Schr\\"odinger equations with long range metrics (JAPANESE)
水谷 治哉 氏 (学習院大学)
Global Strichartz estimates for Schr\\"odinger equations with long range metrics (JAPANESE)
[ 講演概要 ]
We consider Schr\\"odinger equations on the asymptotically Euclidean space
with the long-range condition on the metric.
We show that if the high energy resolvent has at most polynomial growth with respect to the energy,
then global-in-time Strichartz estimates, outside a large compact set, hold.
Under the non-trapping condition we also discuss global-in-space Strichartz estimates.
This talk is based on a joint work with J.-M. Bouclet (Toulouse University).
We consider Schr\\"odinger equations on the asymptotically Euclidean space
with the long-range condition on the metric.
We show that if the high energy resolvent has at most polynomial growth with respect to the energy,
then global-in-time Strichartz estimates, outside a large compact set, hold.
Under the non-trapping condition we also discuss global-in-space Strichartz estimates.
This talk is based on a joint work with J.-M. Bouclet (Toulouse University).
2013年11月19日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
Alexander Pushnitski 氏 (King's Colledge London)
Inverse spectral problem for positive Hankel operators (ENGLISH)
Alexander Pushnitski 氏 (King's Colledge London)
Inverse spectral problem for positive Hankel operators (ENGLISH)
[ 講演概要 ]
Hankel operators are given by (infinite) matrices with entries
$a_{n+m}$ in $\\ell^2$. We consider inverse spectral problem
for bounded self-adjoint positive Hankel operators.
A famous theorem due to Megretskii, Peller and Treil asserts
that such operators may have any continuous spectrum of
multiplicity one or two and any set of eigenvalues of multiplicity
one. However, more detailed questions of inverse spectral
problem, such as the description of isospectral sets, have never
been addressed. In this talk I will describe in detail the
direct and inverse spectral problem for a particular sub-class
of positive Hankel operators. The talk is based on joint work
with Patrick Gerard (Paris, Orsay).
Hankel operators are given by (infinite) matrices with entries
$a_{n+m}$ in $\\ell^2$. We consider inverse spectral problem
for bounded self-adjoint positive Hankel operators.
A famous theorem due to Megretskii, Peller and Treil asserts
that such operators may have any continuous spectrum of
multiplicity one or two and any set of eigenvalues of multiplicity
one. However, more detailed questions of inverse spectral
problem, such as the description of isospectral sets, have never
been addressed. In this talk I will describe in detail the
direct and inverse spectral problem for a particular sub-class
of positive Hankel operators. The talk is based on joint work
with Patrick Gerard (Paris, Orsay).
2013年07月09日(火)
16:30-18:00 数理科学研究科棟(駒場) 118号室
Tom\'as Lungenstrass 氏 (Pontificia Universidad Catolica de Chile)
A Trace Formula for Long-Range Perturbations of the Landau Hamiltonian
(Joint work with Georgi Raikov) (ENGLISH)
Tom\'as Lungenstrass 氏 (Pontificia Universidad Catolica de Chile)
A Trace Formula for Long-Range Perturbations of the Landau Hamiltonian
(Joint work with Georgi Raikov) (ENGLISH)
[ 講演概要 ]
The Landau Hamiltonian describes the dynamics of a two-dimensional
charged particle subject to a constant magnetic field. Its spectrum
consists in eigenvalues of infinite multiplicity given by $B(2q+1)$, $q\\in Z_+$. We
consider perturbations of this operator by including a continuous
electric potential that decays slowly at infinity (as $|x|^{-\\rho}$, $0<\\rho<1$).
The spectrum of the perturbed operator consists of eigenvalue clusters
which accumulate to the Landau levels. We provide estimates for the
rate at which the clusters shrink as we move up the energy levels.
Further, we obtain an explicit description of the asymptotic density
of eigenvalues for asymptotically homogeneous long-range potentials in
terms of a mean-value transform of the associated homogeneous
function.
The Landau Hamiltonian describes the dynamics of a two-dimensional
charged particle subject to a constant magnetic field. Its spectrum
consists in eigenvalues of infinite multiplicity given by $B(2q+1)$, $q\\in Z_+$. We
consider perturbations of this operator by including a continuous
electric potential that decays slowly at infinity (as $|x|^{-\\rho}$, $0<\\rho<1$).
The spectrum of the perturbed operator consists of eigenvalue clusters
which accumulate to the Landau levels. We provide estimates for the
rate at which the clusters shrink as we move up the energy levels.
Further, we obtain an explicit description of the asymptotic density
of eigenvalues for asymptotically homogeneous long-range potentials in
terms of a mean-value transform of the associated homogeneous
function.
2013年05月21日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
上坂 正晃 氏 (東大数理)
Homogenization in a Thin Layer with an Oscillating Interface and Highly Contrast Coefficients (JAPANESE)
上坂 正晃 氏 (東大数理)
Homogenization in a Thin Layer with an Oscillating Interface and Highly Contrast Coefficients (JAPANESE)
[ 講演概要 ]
We consider the homogenization problem of the elliptic boundary value problem in a thin domain which has a high and low conductivity zones. In our model, two media are separated by a highly oscillating interface. The asymptotic behavior is governed by the order of the thickness of the domain, oscillation period of the interface and contrast between two media. In this talk, we show that the limit problem is changed by these parameters. We also introduce the two-scale convergence result in a thin domain which is the key ingredient of the proof.
We consider the homogenization problem of the elliptic boundary value problem in a thin domain which has a high and low conductivity zones. In our model, two media are separated by a highly oscillating interface. The asymptotic behavior is governed by the order of the thickness of the domain, oscillation period of the interface and contrast between two media. In this talk, we show that the limit problem is changed by these parameters. We also introduce the two-scale convergence result in a thin domain which is the key ingredient of the proof.
2012年12月11日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
講演中止になりました.
Rafe Mazzeo 氏 (Stanford University)
This talk was cancelled! (JAPANESE)
講演中止になりました.
Rafe Mazzeo 氏 (Stanford University)
This talk was cancelled! (JAPANESE)
2012年12月04日(火)
16:30-18:30 数理科学研究科棟(駒場) 128号室
Alexander Vasiliev 氏 (Department of Mathematics, University of Bergen, Norway) 16:30-17:30
Evolution of smooth shapes and the KP hierarchy (ENGLISH)
Group of diffeomorphisms of the unit circle and sub-Riemannian geometry (ENGLISH)
Alexander Vasiliev 氏 (Department of Mathematics, University of Bergen, Norway) 16:30-17:30
Evolution of smooth shapes and the KP hierarchy (ENGLISH)
[ 講演概要 ]
We consider a homotopic evolution in the space of smooth
shapes starting from the unit circle. Based on the Loewner-Kufarev
equation we give a Hamiltonian formulation of this evolution and
provide conservation laws. The symmetries of the evolution are given
by the Virasoro algebra. The 'positive' Virasoro generators span the
holomorphic part of the complexified vector bundle over the space of
conformal embeddings of the unit disk into the complex plane and
smooth on the boundary. In the covariant formulation they are
conserved along the Hamiltonian flow. The 'negative' Virasoro
generators can be recovered by an iterative method making use of the
canonical Poisson structure. We study an embedding of the
Loewner-Kufarev trajectories into the Segal-Wilson Grassmannian,
construct the tau-function, the Baker-Akhiezer function, and finally,
give a class of solutions to the KP hierarchy, which are invariant on
Loewner-Kufarev trajectories.
Irina Markina 氏 (Department of Mathematics, University of Bergen, Norway) 17:30-18:30We consider a homotopic evolution in the space of smooth
shapes starting from the unit circle. Based on the Loewner-Kufarev
equation we give a Hamiltonian formulation of this evolution and
provide conservation laws. The symmetries of the evolution are given
by the Virasoro algebra. The 'positive' Virasoro generators span the
holomorphic part of the complexified vector bundle over the space of
conformal embeddings of the unit disk into the complex plane and
smooth on the boundary. In the covariant formulation they are
conserved along the Hamiltonian flow. The 'negative' Virasoro
generators can be recovered by an iterative method making use of the
canonical Poisson structure. We study an embedding of the
Loewner-Kufarev trajectories into the Segal-Wilson Grassmannian,
construct the tau-function, the Baker-Akhiezer function, and finally,
give a class of solutions to the KP hierarchy, which are invariant on
Loewner-Kufarev trajectories.
Group of diffeomorphisms of the unit circle and sub-Riemannian geometry (ENGLISH)
[ 講演概要 ]
We consider the group of sense-preserving diffeomorphisms of the unit
circle and its central extension - the Virasoro-Bott group as
sub-Riemannian manifolds. Shortly, a sub-Riemannian manifold is a
smooth manifold M with a given sub-bundle D of the tangent bundle, and
with a metric defined on the sub-bundle D. The different sub-bundles
on considered groups are related to some spaces of normalized
univalent functions. We present formulas for geodesics for different
choices of metrics. The geodesic equations are generalizations of
Camassa-Holm, Huter-Saxton, KdV, and other known non-linear PDEs. We
show that any two points in these groups can be connected by a curve
tangent to the chosen sub-bundle. We also discuss the similarities and
peculiarities of the structure of sub-Riemannian geodesics on infinite
and finite dimensional manifolds.
We consider the group of sense-preserving diffeomorphisms of the unit
circle and its central extension - the Virasoro-Bott group as
sub-Riemannian manifolds. Shortly, a sub-Riemannian manifold is a
smooth manifold M with a given sub-bundle D of the tangent bundle, and
with a metric defined on the sub-bundle D. The different sub-bundles
on considered groups are related to some spaces of normalized
univalent functions. We present formulas for geodesics for different
choices of metrics. The geodesic equations are generalizations of
Camassa-Holm, Huter-Saxton, KdV, and other known non-linear PDEs. We
show that any two points in these groups can be connected by a curve
tangent to the chosen sub-bundle. We also discuss the similarities and
peculiarities of the structure of sub-Riemannian geodesics on infinite
and finite dimensional manifolds.
2012年11月06日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
Thierry Ramond 氏 (Univ. Paris, Orsay)
Resonance free domains for homoclinic orbits (ENGLISH)
Thierry Ramond 氏 (Univ. Paris, Orsay)
Resonance free domains for homoclinic orbits (ENGLISH)
2012年10月30日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
Francis Nier 氏 (Univ. Rennes 1)
About the method of characteristics (ENGLISH)
Francis Nier 氏 (Univ. Rennes 1)
About the method of characteristics (ENGLISH)
[ 講演概要 ]
While studying the mean field dynamics of a systems of bosons, one is led to solve a transport equation for a probability measure in an infinite dimensional phase-space. Since those probability measures are characterized after testing with cylindrical or polynomial observables, which make classes which are not invariant after composing with a nonlinear flow. Thus the standard method of characteristics for transport equations cannot be extended at once to the infinite dimensional case. A solution comes from techniques developed for optimal transport and a probabilistic interpretation of trajectories.
While studying the mean field dynamics of a systems of bosons, one is led to solve a transport equation for a probability measure in an infinite dimensional phase-space. Since those probability measures are characterized after testing with cylindrical or polynomial observables, which make classes which are not invariant after composing with a nonlinear flow. Thus the standard method of characteristics for transport equations cannot be extended at once to the infinite dimensional case. A solution comes from techniques developed for optimal transport and a probabilistic interpretation of trajectories.
2012年10月23日(火)
16:30-18:00 数理科学研究科棟(駒場) 002号室
Elliott Lieb 氏 (Princeton Univ.)
Topics in quantum entropy and entanglement (ENGLISH)
Elliott Lieb 氏 (Princeton Univ.)
Topics in quantum entropy and entanglement (ENGLISH)
[ 講演概要 ]
Several recent results on quantum entropy and the uncertainty
principle will be discussed. This is partly joint work with Eric Carlen
on lower bounds for entanglement, which has no classical analog, in terms
of the negative of the conditional entropy, S1 - S12, whose negativity,
when it occurs, also has no classical analog. (see arXiv:1203.4719)
It is also partly joint work with Rupert Frank on the uncertaintly
principle for quantum entropy which compares the quantum von Neumann
entropy with the classical entropies with respect to two different
bases. We prove an extension to the product of two and three spaces, which
has applications in quantum information theory. (see arxiv:1204.0825)
Several recent results on quantum entropy and the uncertainty
principle will be discussed. This is partly joint work with Eric Carlen
on lower bounds for entanglement, which has no classical analog, in terms
of the negative of the conditional entropy, S1 - S12, whose negativity,
when it occurs, also has no classical analog. (see arXiv:1203.4719)
It is also partly joint work with Rupert Frank on the uncertaintly
principle for quantum entropy which compares the quantum von Neumann
entropy with the classical entropies with respect to two different
bases. We prove an extension to the product of two and three spaces, which
has applications in quantum information theory. (see arxiv:1204.0825)
2012年07月17日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
菅 徹 氏 (東北大学)
2次元円環領域におけるLiouville-Gel\\'fand方程式の非球対称解の構造 (JAPANESE)
菅 徹 氏 (東北大学)
2次元円環領域におけるLiouville-Gel\\'fand方程式の非球対称解の構造 (JAPANESE)
[ 講演概要 ]
指数関数を非線形項に持つ非線形楕円型方程式(Liouville-Gel'fand方程式)について考察する。特に2次元の円環領域では、この方程式の非球対称な解が球対称解から分岐する形で現れる。本講演では、この分岐解の分岐図上での大域的な構造に関して得られた結果を紹介する。
指数関数を非線形項に持つ非線形楕円型方程式(Liouville-Gel'fand方程式)について考察する。特に2次元の円環領域では、この方程式の非球対称な解が球対称解から分岐する形で現れる。本講演では、この分岐解の分岐図上での大域的な構造に関して得られた結果を紹介する。
2012年07月10日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
牛越 惠理佳 氏 (東北大学)
Hadamard variational formula for the Green function
of the Stokes equations with the boundary condition (JAPANESE)
牛越 惠理佳 氏 (東北大学)
Hadamard variational formula for the Green function
of the Stokes equations with the boundary condition (JAPANESE)
[ 講演概要 ]
本講演では、遅い非圧縮粘性流体の運動を記述したStokes方程式におけるHadamard変分公式の導出について考察する。ここで、Hadamard変分公式とは、1908年にHadamardによって提唱された、領域にある摂動をさせた時に、Green函数に代表される領域に依存する函数が、どのような摂動をするのかを表現したものである。
変分公式は、領域摂動に伴う固有値の漸近挙動を明示的に表現したWeylの漸近公式と関連があるなど、領域摂動問題において大変有用なものとして導出されてきた。本講演において、まずは導入として、楕円型方程式で最も基本的なラプラス方程式のDirichlet問題に対する変分公式について言及し、その後に主結果であるStokes方程式におけるHadamard変分公式について述べる。
本講演では、遅い非圧縮粘性流体の運動を記述したStokes方程式におけるHadamard変分公式の導出について考察する。ここで、Hadamard変分公式とは、1908年にHadamardによって提唱された、領域にある摂動をさせた時に、Green函数に代表される領域に依存する函数が、どのような摂動をするのかを表現したものである。
変分公式は、領域摂動に伴う固有値の漸近挙動を明示的に表現したWeylの漸近公式と関連があるなど、領域摂動問題において大変有用なものとして導出されてきた。本講演において、まずは導入として、楕円型方程式で最も基本的なラプラス方程式のDirichlet問題に対する変分公式について言及し、その後に主結果であるStokes方程式におけるHadamard変分公式について述べる。
2012年06月26日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
伊藤 健一 氏 (筑波大学)
Absence of embedded eigenvalues for the Schr\\"odinger operator on manifold with ends (JAPANESE)
伊藤 健一 氏 (筑波大学)
Absence of embedded eigenvalues for the Schr\\"odinger operator on manifold with ends (JAPANESE)
[ 講演概要 ]
We consider a Riemannian manifold with, at least, one expanding end, and prove the absence of $L^2$-eigenvalues for the Schr\\"odinger operator above some critical value. The critical value is computed from the volume growth rate of the end and the potential behavior at infinity. The end structure is formulated abstractly in terms of some convex function, and the examples include asymptotically Euclidean and hyperbolic ends. The proof consists of a priori superexponential decay estimate for eigenfunctions and the absence of superexponentially decaying eigenfunctions, both of which employs the Mourre-type commutator argument. This talk is based on the recent joint work with E.Skibsted (Aarhus University).
We consider a Riemannian manifold with, at least, one expanding end, and prove the absence of $L^2$-eigenvalues for the Schr\\"odinger operator above some critical value. The critical value is computed from the volume growth rate of the end and the potential behavior at infinity. The end structure is formulated abstractly in terms of some convex function, and the examples include asymptotically Euclidean and hyperbolic ends. The proof consists of a priori superexponential decay estimate for eigenfunctions and the absence of superexponentially decaying eigenfunctions, both of which employs the Mourre-type commutator argument. This talk is based on the recent joint work with E.Skibsted (Aarhus University).
2012年05月22日(火)
16:30-18:00 数理科学研究科棟(駒場) 118号室
この日だけ部屋を118に変更します.
Norbert Pozar 氏 (Graduate School of Mathematical Sciences, The University of Tokyo)
Viscosity solutions for nonlinear elliptic-parabolic problems (ENGLISH)
この日だけ部屋を118に変更します.
Norbert Pozar 氏 (Graduate School of Mathematical Sciences, The University of Tokyo)
Viscosity solutions for nonlinear elliptic-parabolic problems (ENGLISH)
[ 講演概要 ]
We introduce a notion of viscosity solutions for a general class of
elliptic-parabolic phase transition problems. These include the
Richards equation, which is a classical model in filtration theory.
Existence and uniqueness results are proved via the comparison
principle. In particular, we show existence and stability properties
of maximal and minimal viscosity solutions for a general class of
initial data. These results are new even in the linear case, where we
also show that viscosity solutions coincide with the regular weak
solutions introduced in [Alt&Luckhaus 1983]. This talk is based on a
recent work with Inwon Kim.
We introduce a notion of viscosity solutions for a general class of
elliptic-parabolic phase transition problems. These include the
Richards equation, which is a classical model in filtration theory.
Existence and uniqueness results are proved via the comparison
principle. In particular, we show existence and stability properties
of maximal and minimal viscosity solutions for a general class of
initial data. These results are new even in the linear case, where we
also show that viscosity solutions coincide with the regular weak
solutions introduced in [Alt&Luckhaus 1983]. This talk is based on a
recent work with Inwon Kim.
2012年05月15日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
水谷 治哉 氏 (京都大学・数理解析研究所)
Strichartz estimates for Schr\\"odinger equations with variable coefficients and unbounded electromagnetic potentials (JAPANESE)
水谷 治哉 氏 (京都大学・数理解析研究所)
Strichartz estimates for Schr\\"odinger equations with variable coefficients and unbounded electromagnetic potentials (JAPANESE)
[ 講演概要 ]
In this talk we consider the Cauchy problem for Schr\\"odinger equations with variable coefficients and unbounded potentials. Under the assumption that the Hamiltonian is a long-range perturbation of the free Schr\\"odinger operator, we construct an outgoing parametrix for the propagator near infinity, and give applications to sharp Strichartz estimates. The basic idea is to combine the standard approximation by using a time dependent modifier, which is not in the semiclassical regime, with the semiclassical approximation of Isozaki-Kitada type. We also show near sharp Strichartz estimates without asymptotic conditions by using local smoothing effects.
In this talk we consider the Cauchy problem for Schr\\"odinger equations with variable coefficients and unbounded potentials. Under the assumption that the Hamiltonian is a long-range perturbation of the free Schr\\"odinger operator, we construct an outgoing parametrix for the propagator near infinity, and give applications to sharp Strichartz estimates. The basic idea is to combine the standard approximation by using a time dependent modifier, which is not in the semiclassical regime, with the semiclassical approximation of Isozaki-Kitada type. We also show near sharp Strichartz estimates without asymptotic conditions by using local smoothing effects.
2012年02月14日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
Michael Loss 氏 (Georgia Institute of Technology)
Symmetry results for Caffarelli-Kohn-Nirenberg inequalities (ENGLISH)
Michael Loss 氏 (Georgia Institute of Technology)
Symmetry results for Caffarelli-Kohn-Nirenberg inequalities (ENGLISH)
2012年01月31日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
Michel Chipot 氏 (University of Zurich)
Obstacle problems in unbounded domains (ENGLISH)
Michel Chipot 氏 (University of Zurich)
Obstacle problems in unbounded domains (ENGLISH)
[ 講演概要 ]
We will present a formulation of obstacle problems in unbounded
domains when the energy method does not work, i.e. whenthe force does not belong to H^{-1}.
We will present a formulation of obstacle problems in unbounded
domains when the energy method does not work, i.e. whenthe force does not belong to H^{-1}.
2011年12月20日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
Gueorgui Raykov 氏 (Catholic University of Chile)
A trace formula for the perturbed Landau Hamiltonian (ENGLISH)
Gueorgui Raykov 氏 (Catholic University of Chile)
A trace formula for the perturbed Landau Hamiltonian (ENGLISH)
[ 講演概要 ]
The talk will be based on a joint work with A. Pushnitski
and C. Villegas-Blas, the preprint is available here:
http://arxiv.org/abs/1110.3098 .
The talk will be based on a joint work with A. Pushnitski
and C. Villegas-Blas, the preprint is available here:
http://arxiv.org/abs/1110.3098 .
2011年12月13日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
Wolfram Bauer 氏 (ゲッチンゲン大学)
Trivializable subriemannian structures and spectral analysis of associated operators (ENGLISH)
Wolfram Bauer 氏 (ゲッチンゲン大学)
Trivializable subriemannian structures and spectral analysis of associated operators (ENGLISH)
2011年11月08日(火)
16:30-18:00 数理科学研究科棟(駒場) 128号室
寺澤 祐高 氏 (東京大数理（日本学術振興会特別研究員PD）)
確率的摂動項を持つ冪乗法則流体方程式の弱解の存在と 一意性について (JAPANESE)
寺澤 祐高 氏 (東京大数理（日本学術振興会特別研究員PD）)
確率的摂動項を持つ冪乗法則流体方程式の弱解の存在と 一意性について (JAPANESE)
[ 講演概要 ]
本講演では、非圧縮性非ニュートン流体の運動を記述する
偏微分方程式に加法的確率的摂動項を加えた確率偏微分方程式 の弱解
の存在と一意性について考察する。 非ニュートン流体としては、粘性
が変形速度テンソルの大きさの冪乗 の形で依存する冪乗法則流体を考
察し、確率的摂動項としては 有色雑音を考察する。 Necas-Malek-
Ruzicka('93)において、確率的外力項を伴わない、 決定方程式に関し
て示された弱解の存在と一意性の主張を、 確率的摂動項を持つ方程式
に対して示す。 解の存在の証明は、ガレルキン近似によって得られた
解の列に対して、 伊藤の公式、Birkholder-Davis-Gundyの不等式など
により、 解の列のコンパクト性を示すこと及び、解の部分列が収束し
、 その収束先が方程式を弱い意味で満たすことを示すことでなされる。
なお、本講演は、吉田伸生氏(京都大学)との共同研究に基づく。
本講演では、非圧縮性非ニュートン流体の運動を記述する
偏微分方程式に加法的確率的摂動項を加えた確率偏微分方程式 の弱解
の存在と一意性について考察する。 非ニュートン流体としては、粘性
が変形速度テンソルの大きさの冪乗 の形で依存する冪乗法則流体を考
察し、確率的摂動項としては 有色雑音を考察する。 Necas-Malek-
Ruzicka('93)において、確率的外力項を伴わない、 決定方程式に関し
て示された弱解の存在と一意性の主張を、 確率的摂動項を持つ方程式
に対して示す。 解の存在の証明は、ガレルキン近似によって得られた
解の列に対して、 伊藤の公式、Birkholder-Davis-Gundyの不等式など
により、 解の列のコンパクト性を示すこと及び、解の部分列が収束し
、 その収束先が方程式を弱い意味で満たすことを示すことでなされる。
なお、本講演は、吉田伸生氏(京都大学)との共同研究に基づく。
