## PDE実解析研究会

開催情報 火曜日　10:30～11:30　数理科学研究科棟(駒場) 056号室 儀我美一、石毛和弘、三竹大寿、米田剛 http://coe.math.sci.hokudai.ac.jp/sympo/pde_ra/ 首都圏の偏微分方程式、実解析の研究をさらに活発にするために本研究会を東大で開催いたします。偏微分方程式研究者と実解析研究者の討論がより日常的になることを目指しています。そのため、講演がその分野の概観をもわかるような形になるよう配慮いたします。また講演者との1対1の討論がしやすいように講演は火曜の午前とし、午後に討論用の場所を用意いたします。この研究会を通して皆様に気楽に東大を訪問していただければ幸いです。北海道大学のHPには、第1回(2004年9月29日)～第38回(2008年10月15日)の情報が掲載されております。

### 2012年12月05日(水)

10:30-11:30   数理科学研究科棟(駒場) 002号室

Jie Jiang 氏 (Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences)
Convergence to Equilibrium of Bounded Solutions with Application of Lojasiewicz-Simon's inequality (ENGLISH)
[ 講演概要 ]
In this talk, we present the application of Lojasiewicz-Simon's inequality to the study on convergence of bounded global solutions to some evolution equations. We take a semi-linear parabolic initial-boundary problem as an example. With the help of Lojasiewicz-Simon's inequality we prove that the bounded global solution will converge to an equilibrium as time goes to infinity provided the nonlinear term is analytic in the unknown function. We also present the application of Lojasiewicz-Simon's inequality to the asymptotic behavior studies on phase-field models with Cattaneo law and chemotaxis models with volume-filling effect.

### 2012年11月21日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Giovanni Pisante 氏 (Seconda Università degli Studi di Napoli)
Shape Optimization And Asymptotic For The Twisted Dirichlet Eigenvalue (ENGLISH)
[ 講演概要 ]
Aim of the talk is to discuss some recent results obtained with G. Croce and A. Henrot on a generalization of the functional defining the first twisted eigenvalue.
We look at the set functional defined by minimizing a Rayleigh quotient involving Lebesgue norms with different exponents p and q among functions satisfying a zero boundary condition as well as a zero mean condition of order q.
First under suitable conditions on p and q, that ensure the existence of a minimizing function, we investigate the validity of an isoperimetric type inequality of the Reyleigh-Faber-Krahn type.
Then we study the limit of the functional for p and q tending to 1 and to infinity and discuss the relation with the limits of the second eigenvalues of the p-laplacian operator.

### 2012年06月20日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Paolo Maremonti 氏 (Seconda Università degli Studi di Napoli)
On the Navier-Stokes Cauchy problem with nondecaying data (ENGLISH)
[ 講演概要 ]
We prove the well posedeness of the Navier-Stokes Cauchy problem for nondecaying initial data u_0 \\in C (R^n) \\cap L^\\infty (R^n), n >= 3. This problem is studied by Giga, Inui and Matsui for n >= 3, and Giga, Matsui and Sawada in the two dimensional case. The aims of our paper are slight different since we also find pointwise estimates for the pressure field. Via a uniqueness theorem, we give a sort of structure theorem to GIM solutions.

### 2012年05月23日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Xingfei Xiang 氏 (East China Normal University)
$L^p$ Estimates of the Vector Fields and their Applications (ENGLISH)
[ 講演概要 ]
For $1< p < \\infty$, the estimates of $W^{1,p}$ norm of the vector fields in bounded domains in $\\mathbb R^3$ in terms of their divergence and curl have been well studied. In this talk, we shall present the $L^{{3}/{2}}$ estimates of vector fields with the $L^1$ norm of the $\\curl$ in bounded domains. By a similar discussion, we establish the $L^p$ estimates of the vector fields for $1 < p < \\infty$. As an application of the $L^p$ estimates, the Global $\\dv-\\curl$ lemma in Sobolev spaces of negative indices is given.

### 2012年04月04日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Jens Hoppe 氏 (Sogang University / KTH Royal Institute of Technology)
Multi linear formulation of differential geometry and matrix regularizations (ENGLISH)
[ 講演概要 ]
We prove that many aspects of the differential geometry of embedded Riemannian manifolds can be formulated in terms of multi linear algebraic structures on the space of smooth functions. In particular, we find algebraic expressions for Weingarten's formula, the Ricci curvature and the Codazzi-Mainardi equations.
For matrix analogues of embedded surfaces we define discrete curvatures and Euler characteristics, and a non-commutative Gauss–Bonnet theorem is shown to follow. We derive simple expressions for the discrete Gauss curvature in terms of matrices representing the embedding coordinates, and a large class of explicit examples is provided.

### 2012年03月21日(水)

10:00-11:00   数理科学研究科棟(駒場) 056号室

Chiun-Chang Lee 氏 (National Taiwan University)
The asymptotic behaviors of the solutions of Poisson-Boltzmann type of equations (ENGLISH)
[ 講演概要 ]
Understanding the existence of electrical double layers around particles in the colloidal dispersion (system) is a crucial phenomenon of the colloid science. The Poisson-Boltzmann (PB) equation is one of the most widely used models to describe the equilibrium phenomenon of an electrical double layer in colloidal systems. This motivates us to study the asymptotic behavior for the boundary layer of the solutions of the PB equation. In this talk, we introduce the precise asymptotic formulas for the slope of the boundary layers with the exact leading order term and the second-order term. In particular, these formulas show that the mean curvature of the boundary exactly appears in the second-order term. This part is my personal work.
On the other hand, to study how the ionic concentrations and ionic valences affect the difference between the boundary and interior potentials in an electrolyte solution, we also introduce a modified PB equation - New Poisson-Boltzmann (PB_n) equation - joint works with Prof. Tai-Chia Lin and Chun Liu and YunKyong Hyon. We give a specific formula showing the influence of these crucial physical quantities on the potential difference in an electrolyte solution. This cannot be found in the PB equation.

### 2012年03月14日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Jürgen Saal 氏 (Technische Universität Darmstadt)
Exponential convergence to equilibria for a general model in hydrodynamics (ENGLISH)
[ 講演概要 ]
We present a thorough analysis of the Navier-Stokes-Nernst-Planck-Poisson equations. This system describes the dynamics of charged particles dispersed in an incompressible fluid.
In contrast to existing literature and in view of its physical relevance, we also allow for different diffusion coefficients of the charged species.
In addition, the commonly assumed electro-neutrality condition is not required by our approach.
Our aim is to present results on local and global well-posedness as well as exponential stability of equilibria. The results are obtained jointly with Dieter Bothe and Andre Fischer at the Center of Smart Interfaces at TU Darmstadt.

### 2012年02月01日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Chun Liu 氏 (University of Tokyo / Penn State University)
Energetic variational approach: generalized diffusion, stochastic differential equations and optimal transport (ENGLISH)
[ 講演概要 ]
In the talk, I will explore the general framework of energetic variational approaches, which are the direct consequences of classical isothermal thermodynamics, and their particular applications in generalized diffusion problems. In particular, we reveal the roles of different stochastic integrations (Ito's form, Stratonovich's form and other possible forms) and the Wasserstein metric and the procedure of optimal transport in the context of general framework of theories of linear responses.

### 2011年10月31日(月)

13:30-14:30   数理科学研究科棟(駒場) 056号室

Horst Heck
Stationary Weak Solutions of the Navier-Stokes Equations Past an Obstacle (ENGLISH)
[ 講演概要 ]
Consider the stationary Navier-Stokes equations in an exterior smooth domain $\\Omega$. If the flow condition $u_\\infty$ for $u$ at infinity is non-zero and the external force $f\\in \\dot H^{-1}_2(\\Omega)$ is given Leray constructed a weak solution $u\\in \\dot H^1_2(\\Omega)$, the homogeneous Sobolev space, with $u-u_\\infty\\in L^6(\\Omega)$.
We show that if in addition $f\\in \\dot H^{-1}_q(\\Omega)$ for some $q\\in (4/3,4)$ then the weak solution has the property $u-u_\\infty\\in L^{4q/(4-q)}(\\Omega)$.
This additional integrability implies that $u$ satisfies the energy identity. Further consequences are uniqueness results for small $u_\\infty$ and $f$ and continuous dependence of the solution with respect to $u_\\infty$.
The presented results are joint work with Hyunseok Kim and Hideo Kozono.

### 2011年07月06日(水)

10:00-11:00   数理科学研究科棟(駒場) 056号室

trace不等式とMorrey空間 (JAPANESE)
[ 講演概要 ]
この講演では、p乗Lebesgue可積分空間からq乗 \\mu 測度可積分空間へ分数積分作用素を有界とする測度 \\mu の条件を記述する不等式を、「trace不等式」と呼ぶ。

### 2011年04月20日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Stochastic power law fluids (JAPANESE)
[ 講演概要 ]
This talk is based in part on a joint work with Yutaka Terasawa.
We consider a SPDE (stochastic partial differential equation) which describes the velocity field of a viscous, incompressible non-Newtonian fluid subject to a random force.
Here, the extra stress tensor of the fluid is given by a polynomial of degree $p-1$ of the rate of strain tensor, while the colored noise is considered as a random force.
We first investigate the existence and the uniqueness of weak solutions to this SPDE.
We next turn to the special case: $p \\in [1 + {d \\over 2},{2d\\overd-2})$,
where $d$ is the dimension of the space. We prove there that the Galerkin scheme approximates the velocity field in a strong sense. As a consequence, we establish the energy equality for the velocity field.
[ 参考URL ]
http://www.math.kyoto-u.ac.jp/~nobuo/

### 2011年01月26日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Jong-Shenq Guo 氏 (Department of Mathematics, Tamkang University
)
Quenching Problem Arising in Micro-electro Mechanical Systems

(JAPANESE)
[ 講演概要 ]
In this talk, we shall present some recent results on quenching problems which arise in Micro-electro Mechanical Systems.
We shall also give some open problems in this research area.

### 2010年05月26日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Giovanni Pisante 氏 (Department of Mathematics
Hokkaido University)
A SELECTION CRITERION FOR SOLUTIONS OF A
SYSTEM OF EIKONAL EQUATIONS
(ENGLISH)
[ 講演概要 ]
We deal with the system of eikonal equations |ðu/ðx1|=1, |ðu/ðx2|=1 in a planar Lipschitz domain with zero boundary condition. Exploiting the classical pyramidal construction introduced by Cellina, it is easy to prove that there exist infinitely many Lipschitz solutions. Then, the natural problem that has arisen in this framework is to find a way to select and characterize a particular meaningful class of solutions.
We propose a variational method to select the class of solutions which minimize the discontinuity set of the gradient. More precisely we select an optimal weighted measure for the jump set of the second derivatives of a given solution v of the system and we prove the existence of minimizers of the corresponding variational problem.

### 2010年05月12日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Jean-Pierre Puel 氏 (Graduate School of Mathematical Sciences
The University of Tokyo)
Exact controllability for incompressible fluids (ENGLISH)
[ 講演概要 ]
After a short presentation of J.-M. Coron's results for Euler equation, we will give the good notions of controllability for Navier-Stokes equations, namely the exact controllability to trajectories.
We will outline the strategy for obtaining local results, based on a fixed point argument following the study of null controllability for the linearized problem. This is equivalent to an observability inequality for the adjoint system, which requires a global Carleman estimate for linearized Navier-Stokes equations. We will explain this estimate and the different steps for obtaining it along the lines of the articles by E.Fernadez-Cara, S.Guerrero, O.Imanuvilov and J.-P.Puel (JMPA, 2004) and M.Gonzalez-Burgos, S.Guerrero and J.-P.Puel (CPAA, 2009).
We will end up with some important open problems.

### 2010年04月28日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Marcus Wunsch 氏 (Kyoto University
)
GLOBAL AND SINGULAR SOLUTIONS TO SOME
HYDRODYNAMIC EVOLUTION EQUATIONS
[ 講演概要 ]
The two-component Hunter-Saxton system is a recently derived system of evolution equations modeling, e.g., the nonlinear dynamics of nondissipative dark matter and the propagation of orientation waves in nematic liquid crystals. It is imbedded into a parameterized family of systems called the generalized Hunter-Saxton (2HS) system [2] reducing, if one component is omitted, to the generalized Proudman-Johnson(gPJ) equation [1] modeling three-dimensional vortex dynamics.
After demonstrating, by means of Kato's semigroup theory, the local-in-time existence of classical solutions, the blow-up scenarios for the 2HS system and the gPJ equation are described. The explicit construction of weak dissipative solutions for both models is discussed in detail.
Finally, global existence in time of these weak solutions is proved.

### 2010年03月09日(火)

10:30-11:30   数理科学研究科棟(駒場) 123号室

Joachim Escher 氏 (Leibniz University of Hanover)
Shallow water waves with singularities
[ 講演概要 ]
The Degasperis-Procesi equation is a recently derived shallow water wave equation, which is - similar as the Camassa-Holm equation - embedded in a family of spatially periodic third order dispersive conservation laws.
The coexistence of globally in time defined classical solutions, wave breaking solutions, and spatially periodic peakons and shock waves is evidenced in the talk, and the precise blow-up scenario, including blow-up rates and blow-up sets, is discussed in detail. Finally several conditions on the initial profile are presented, which ensure the occurence of a breaking wave.

### 2009年12月02日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Juergen Saal 氏 (University of Konstanz)
A hyperbolic fluid model based on Cattaneo's law
[ 講演概要 ]
In various applications a delay of the propagation speed of a fluid (temperature, ...) has been observed. Such phenomena cannot be described by standard parabolic models, whose derivation relies on Fourier's law (Paradoxon of infinite propagation speed).
One way to give account to these observations and which was successfully applied to several models, is to replace Fourier's law by the law of Cattaneo. In the case of a fluid, this leads to a hyperbolicly perturbed quasilinear Navier-Stokes system for which existence and uniqueness results will be presented.

### 2009年11月25日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Recent results on weak and strong solutions of the Navier-Stokes equations
[ 講演概要 ]
Our purpose is to develop the optimal initial value condition for the existence of a unique local strong solution of the Navier-Stokes equations in a smooth bounded domain.

This condition is not only sufficient
- there are several well-known sufficient conditions in this context
- but also necessary, and yields therefore the largest possible class of such strong solutions.

As an application we obtain several extensions of Serrin's regularity condition. A restricted result also holds for completely general domains. Furthermore we extend the well-known class of Leray-Hopf weak solutions with zero boundary conditions and zero divergence to a larger class with corresponding nonzero conditions.

### 2009年10月07日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Wiener measure and Feynman-Kac formula on the Heisenberg group
[ 講演概要 ]
It is well known that the Feynman-Kac formula on the Euclidean space gives the solution of Schrodinger equation by the Wiener integral. We will discuss the Wiener measure and Feynman-Kac formula on the Heisenberg group. The results hold on the H-type groups.

### 2009年06月24日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Winston Ou 氏 (Scripps College / currently visiting assistant professor at Keio University)
Monge-Ampere equations, the Bellman Function Technique, and Muckenhoupt weights
[ 講演概要 ]
In the last few years several classical results in harmonic analysis (in particular, the study of $A_\\infty$ weights have been sharpened with the use of a version of the Bellman function method (promulgated by Nazarov, Treil, and Volberg in the 90's) that involves recognizing the Bellman function as the solution of a Monge-Ampere PDE (the method was introduced by Vasyunin in 2003). We will give a sketch of the modified technique, outline some recent work-in-progress (with Slavin and Wall) using the technique in $A_\\infty$, and then present a few related problems.

### 2009年06月17日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Variational problems for anisotropic surface energies
[ 講演概要 ]
A surface energy is anisotropic if it depends on the direction of the surface. The minimizer of an anisotropic surface energy among all closed surfaces enclosing a fixed volume is called the Wulff shape. We will discuss the characterization of the Wulff shape, the uniqueness and stability of solutions to variational problems for anisotropic surface energy with several boundary conditions.

### 2009年05月20日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Stability of the Burgers vortex
[ 講演概要 ]
The Burgers vortex is an exact vortex solution to the three dimensional stationary Navier-Stokes equations for viscous incompressible fluids in the presence of an axisymmetric background straining flow. In this talk we discuss the stability of the Burgers vortex with respect to two or three dimensional perturbation flows.

### 2009年04月22日(水)

10:30-11:30   数理科学研究科棟(駒場) 128号室
いつもとは会場が異なります。
Wilhelm Klingenberg 氏 (University of Durham)
From Codazzi-Mainardi to Cauchy-Riemann
[ 講演概要 ]
In joint work with Brendan Guilfoyle we established an upper bound for the winding number of the principal curvature foliation at any isolated umbilic of a surface in Euclidean three-space. In our talk, we will focus on the analytic core of the problem. Here is a model of the triaxial ellipsoid with its curvature foliation and one umbilic on the right.

### 2008年10月15日(水)

10:30-11:30   数理科学研究科棟(駒場) 056号室

Asymptotic behavior of solutions for BCF model describing crystal surface growth
[ 講演概要 ]
This talk is concerned with the initial-boundary value problem for a nonlinear parabolic equation which was presented Johnson et al. for describing the process of growth of a crystal surface on the
basis of the BCF theory. We will investigate asymptotic behavior of solutions by construct exponential attractors and a Lyapunov function and by examining a structure of the $\\omega$ limit set.

### 2008年06月04日(水)

16:00-18:15   数理科学研究科棟(駒場) 056号室
William Rundell 氏 (Department of Mathematics, Texas A&M University) 16:00-17:00
Inverse Obstacle Recovery when the boundary condition is also unknown
[ 講演概要 ]
We consider the inverse problem of recovering the shape, location
and surface properties of an object where the surrounding medium
is both conductive and homogeneous. It is assumed that the physical situation is modeled by either harmonic functions or solutions of the Helmholtz equation and that the boundary condition on the obstacle is one of impedance type. We measure either Cauchy data, on an accessible part of the exterior boundary or the far field pattern resulting from a plane wave. Given sets of Cauchy data pairs we wish to recover both the shape and location of the unknown obstacle together with its impedance.
It turns out this adds considerable complexity to the analysis. We give a local injectivity result and use two different algorithms
to investigate numerical reconstructions. The setting is in two space dimensions, but indications of possible extensions (and difficulties) to three dimensions are provided. We also look at the case of a nonlinear impedance function.
David Colton 氏 (Department of Mathematical Sciences, University of Delaware) 17:15-18:15
The Inverse Scattering Problem for an Isotropic Medium
[ 講演概要 ]
This talk is concerned with the inverse electromagnetic scattering problem for an isotropic inhomogeneous infinite cylinder. After formulating the direct scattering problem we proceed to the inverse scattering problem which is the main theme of this lecture. After discussing what is known about uniqueness for the inverse problem,we will proceed to the definition and properties of the far field operator. This leads to the study of a rather unusual spectral problem for partial differential equations called the interior transmission problem. We will state what is known about this problem including its role in determining lower bounds for the index of refraction from a knowledge of the far field pattern of the scattered wave, The talk is concluded by briefly considering the case of limited aperture data,in particular the use of the gap reciprocity method to determine the shape and location of buried objects. Numerical examples will be given as well as a number of open problems.