Uniqueness for Inverse Boundary Value Problems by Dirichlet-to-Neumann Map on Subboundaries

We consider inverse boundary value problems for elliptic equations of second order of determining coefficients by Dirichlet-to-Neumann map on subboundaries, that is, the mapping from Dirichlet data supported on subboundary ${\partial \Omega \setminus \Gamma_{-}}$ to Neumann data on subboundary ${\partial \Omega \setminus \Gamma_{+}}$ . First we prove uniqueness results in three dimensions under some conditions such as ${\overline{\Gamma_{+}\cup\Gamma_{-}}= \partial\Omega}$ Next we survey uniqueness results in two dimensions for various elliptic systems for arbitrarily given ${\Gamma_{-} = \Gamma_{+}}$ Our proof is based on complex geometric optics solutions which are constructed by a Carleman estimate.     

Insensitizing controls for the parabolic equation with equivalued surface boundary conditions

This paper is devoted to the study of the existence of insensitizing controls for the parabolic equation with equivalued surface boundary conditions. The insensitizing problem consists in finding a control function such that some energy functional of the equation is locally insensitive to a perturbation of the initial data. As usual, this problem can be reduced to a partially null controllability problem for a cascade system of two parabolic equations with equivalued surface boundary conditions. Compared the problems with usual boundary conditions, in the present case we need to derive a new global Carleman estimate, for which, in particular one needs to construct a new weight function to match the equivalued surface boundary conditions.     

ASYMPTOTIC BEHAVIOR FOR A CLASS OF ELLIPTIC EQUIVALUED SURFACE BOUNDARY VALUE PROBLEM WITH DISCONTINUOUS INTERFACE CONDITIONS

Spontaneous potential well-logging is one of the important techniques in petroleum exploitation. A spontaneous potential satisfies an elliptic equivalued surface boundary value problem with diseontinuous interface conditlons. In practice, the measuring electrode is so small that we can simplify the corresponding equivalued surface to a point. In this paper, we give a positive answer to this approximation process: when the equivalued surface shrinks to a point, the solution of the original equivalued surface boundary value problem converges to the solution of the corresponding limit boundary value problem.     

The behaviour of microstructures with small shears of the austenite-martensite interface in martensitic phase transformations

Let $\Omega \subset \Bbb{R}^2$ denote a bounded domain whose boundary $\partial \Omega$ is Lipschitz and contains a segment $\Gamma_0$ representing the austenite-twinned martensite interface. We prove $$\displaystyle{\inf_{{u\in \cal W}(\Omega)} \int_\Omega \varphi(\nabla u(x,y))dxdy=0}$$ for any elastic energy density $\varphi : \Bbb{R}^2 \rightarrow [0,\infty)$ such that $\varphi(0,\pm 1)=0$. Here ${\cal W}(\Omega)$ consists of all Lipschitz functions $u$ with $u=0$ on $\Gamma_0$ and $|u_y|=1$ a.e. Apart from the trivial case $\Gamma_0 \subset \reel \times \{a\},~a\in \Bbb{R}$, this result is obtained through the construction of suitable minimizing sequences which differ substantially for vertical and non-vertical segments.     

Limit behaviour of optimal control problems governed by elliptic boundary value problems with equivalued surface

In this paper, we discuss the limit behaviour of optimal control problems governed by elliptic boundary value problems with equivalued surface when the equivalued surface boundary shrinks to a fixed point on the outer boundary of a bounded domain.     

The Generalized Riemann-Hilbert problem For a Multi-connected Region of Second Order Non-linear Elliptic Equations

In this paper, we consider the generalized Riemann-Hilbert problem for second order non-linear elliptic complex equation $\frac{\partial ^2 w}{\partial \bar z ^2}=F(z,w,\frac{\partial w}{\partial \bar z},\frac{\partial w}{\partial z},\frac{\partial ^2 w}{\partial z \partial \bar z}),z\in G$(1) with the boundary condition $Re[z^-n_1e^-\pii\alpha_1(z)w]=r_1(z),Re[z^-n_2e^\pi i \alpha_2(z) \frac{\partial w}{\partial \bar z}]=r_2(z),z\in \Gamma$ where $\Gamma=\Gamma_0+\Gamma_1+\cdots+\Gamma_m$ is the smooth boundary of a multi-connected region G,$n_i(i=1,2)$ are called the indices of the boundary value problem. we also obtain the following existence theorem of generalized solution. Theorem, suppose that the indices $n_i>m-1$, the coefficients of the complex equation (1) and the boundary condition (2) satisftes the condition (c),and q^0 is sufficiently small, then the seneralized Riemann-Hilbert problem.(1), (2)is solvable and the solution has theexpression (7).     

椭圆问题的非线性边界条件均匀化

在本文我们讨论了在等值面边值问题中的非线性边界条件的均匀化,推广了相应的边界条件均匀化结果,而且可应用到用于处理热敏电阻问题中的一类非线性非局部边值问题的边界条件均匀化问题。     

Limit behaviour of solutions to equivalued surface boundary value problem for p‐Laplacian equations: II

In this paper (which is a continuation of Part‐I), we discuss the limit behaviour of solutions to boundary value problem with equivalued surface for p‐Laplacian equations in the case of 1<p?2?1/N when the equivalued surface boundary shrinks to a point in certain way. Copyright © 2001 John Wiley & Sons, Ltd.     

Stabilization of the damped wave equation with Cauchy–Ventcel boundary conditions

This paper is devoted to the study of uniform energy decay rates of solutions to the wave equation with Cauchy–Ventcel boundary conditions:

Limit behaviour of solutions to equivalued surface boundary value problem for p‐Laplacian equations

In this paper, we discuss the limit behaviour of solutions to boundary value problem with equivalued surface for p‐Laplacian equations when the equivalued surface boundary shrinks to a point in certain way. Copyright © 2000 John Wiley & Sons, Ltd.     

Dynamical system with boundary control associated with a symmetric semibounded operator

Let L ₀ be a closed densely defined symmetric semibounded operator with nonzero defect indices in a separable Hilbert space $\mathcal H$ . It determines a Green system $\{{\mathcal H}, {\mathcal B}; L_0, \Gamma_1, \Gamma_2\}$ , where ${\mathcal B}$ is a Hilbert space, and the $\Gamma_i: {\mathcal H} \to \mathcal B$ are operators connected by the Green formula $$ (L_0^*u, v)_{\mathcal H}-(u,L_0^*v)_{\mathcal H} =(\Gamma_1 u, \Gamma_2 v)_{\mathcal B} - (\Gamma_2 u, \Gamma_1 v)_{\mathcal B}. $$ The boundary space $\mathcal B$ and the boundary operators Γ _i are chosen canonically in the framework of the Vishik theory. With the Green system one associates a dynamical system with boundary control (DSBC): $$ \begin{array}{lll} && u_{tt}+L_0^*u = 0, \quad u(t) \in {\mathcal H}, \quad t>0,\\ && u\big|_{t=0}=u_t\big|_{t=0}=0, \\ && \Gamma_1 u = f, \quad f(t) \in {\mathcal B},\quad t \geq 0. \end{array} $$ We show that this system is controllable if and only if the operator L ₀ is completely non-self-adjoint. A version of the notion of wave spectrum of L ₀ is introduced. It is a topological space determined by L ₀ and constructed from reachable sets of the DSBC. Bibliography: 15 titles.     

Unitary Equivalence of Proper Extensions of a Symmetric Operator and the Weyl Function

Let A be a densely defined simple symmetric operator in ${\mathfrak{H}}$ , let ${\Pi=\{\mathcal{H},\Gamma_0, \Gamma_1}\}$ be a boundary triplet for A ^* and let M(·) be the corresponding Weyl function. It is known that the Weyl function M(·) determines the boundary triplet Π, in particular, the pair {A, A ₀}, uniquely up to the unitary similarity. Here ${A_0 := A^* \upharpoonright \text{ker}\, \Gamma_0 ( = A^*_0)}$ . At the same time the Weyl function corresponding to a boundary triplet for a dual pair of operators defines it uniquely only up to the weak similarity. We consider a symmetric dual pair {A, A} with symmetric ${A \subset A^*}$ and a special boundary triplet ${\widetilde{\Pi}}$ for{A, A} such that the corresponding Weyl function is ${\widetilde{M}(z) = K^*(B-M(z))^{-1} K}$ , where B is a non-self-adjoint bounded operator in ${\mathcal{H}}$ . We are interested in the problem whether the result on the unitary similarity remains valid for ${\widetilde{M}(\cdot)}$ in place of M(·). We indicate some sufficient conditions in terms of the operators A ₀ and ${A_B= A^* \upharpoonright \text{ker}\, (\Gamma_1-B \Gamma_0)}$ , which guaranty an affirmative answer to this problem. Applying the abstract results to the minimal symmetric 2nth order ordinary differential operator A in ${L^2(\mathbb{R}_+)}$ , we show that ${\widetilde{M}(\cdot)}$ defined in ${\Omega_+ \subset \mathbb{C}_+}$ determines the Dirichlet and Neumann realizations uniquely up to the unitary equivalence. At the same time similar result for realizations of Dirac operator fails. We obtain also some negative abstract results demonstrating that in general the Weyl function ${\widetilde{M}(\cdot)}$ does not determine A _B even up to the similarity.     

On the weak solution of the Neumann problem for the 2D Helmholtz equation in a convex cone and Hs regularity

We extend previous results for the Neumann boundary value problem to the case of boundary data from the space $H^{-\frac{1}{2}+\varepsilon}(\Gamma), 0{<}{\varepsilon}{<}\frac{1}{2}We extend previous results for the Neumann boundary value problem to the case of boundary data from the space $H^{-\frac{1}{2}+\varepsilon}(\Gamma), 0{<}{\varepsilon}{<}\frac{1}{2}$, where Γ=?Ω is the boundary of a two‐dimensional cone Ω with angle β<π. We prove that for these boundary conditions the solution of the Helmholtz equation in Ω exists in the Sobolev space H^1+ε(Ω), is unique and depends continuously on the boundary data. Moreover, we give the Sommerfeld representation for these solutions. This can be used to formulate explicit compatibility conditions on the data for regularity properties of the corresponding solution. Copyright © 2010 John Wiley & Sons, Ltd.     

Deformation of -cusp forms

We develop an algorithm for numerical computation of the Eisenstein series on a Riemann surface of constant negative curvature. We focus in particular on the computation of the poles of the Eisenstein series. Using our numerical methods, we study the spectrum of the Laplace-Beltrami operator as the surface is being deformed. Numerical evidence of the destruction of -cusp forms is presented.

     

Exponential Convergence of <Emphasis Type="Italic">hp</Emphasis>-FEM for Elliptic Problems in Polyhedra: Mixed Boundary Conditions and Anisotropic Polynomial Degrees

We prove exponential rates of convergence of hp-version finite element methods on geometric meshes consisting of hexahedral elements for linear, second-order elliptic boundary value problems in axiparallel polyhedral domains. We extend and generalize our earlier work for homogeneous Dirichlet boundary conditions and uniform isotropic polynomial degrees to mixed Dirichlet–Neumann boundary conditions and to anisotropic, which increase linearly over mesh layers away from edges and vertices. In particular, we construct \(H^1\)-conforming quasi-interpolation operators with N degrees of freedom and prove exponential consistency bounds \(\exp (-b\root 5 \of {N})\) for piecewise analytic functions with singularities at edges, vertices and interfaces of boundary conditions, based on countably normed classes of weighted Sobolev spaces with non-homogeneous weights in the vicinity of Neumann edges.     

非交换环的拟零因子图

In this paper, a new class of rings, called FIC rings, is introduced for studying quasi-zero-divisor graphs of rings. Let R be a ring. The quasi-zero-divisor graph of R, denoted by Γ_*(R), is a directed graph defined on its nonzero quasi-zero-divisors, where there is an arc from a vertex x to another vertex y if and only if x Ry = 0. We show that the following three conditions on an FIC ring R are equivalent:(1) χ(R) is finite;(2) ω(R) is finite;(3)Nil_*R is finite where Nil_*R equals the finite intersection of prime ideals. Furthermore, we also completely determine the connectedness, the diameter and the girth of Γ_*(R).     

The Comparison of Asymptotio Behavior of the Solution of Equivalued Boundary Value Problems for Nonlinear and Linear Elliptic Equations

This paper shows the different asymptotic behavior of the solution of equivalued boundary value problems for nonlinear equation from the solution to linear one, while the boundary, on which the equivalued boundary value is carried, shrinks to afixed point.     

The Wave Equation in Lp-Spaces

In the first part of the paper, Gaussian estimates are used to study $L^p$-summability of the solution of the wave equation in $L^p(\Omega)$ associated with a general operator in divergence form with bounded coefficients. Secondly, we prove that if $\Omega$ is a cube in $\RR^N$, then the Laplacian with Dirichlet or Neumann boundary conditions generates an $\al$-times integrated cosine function on $L^p(\Omega),\;1\le p <\infty$ for any $\al\ge (N-1)|\frac{1}{2}-\frac{1}{p}|$.     

Topologically conjugate Kleinian groups

Two Kleinian groups and are said to be topologically conjugate when there is a homeomorphism such that . It is conjectured that if two Kleinian groups and are topologically conjugate, one is a quasi-conformal deformation of the other. In this paper generalizing Minsky's result, we shall prove that this conjecture is true when is finitely generated and freely indecomposable, and the injectivity radii of all points of and are bounded below by a positive constant.

     

一类多重循环群的剩余有限性质

设A是秩为n(n≥2)的自由Abel群,A的自同构群Aut(A)= GL(n,Z).对整数m,取 α =(0 1 0…0 0 0(………)(…………)0 0 0…0 1 1 0…0 m)∈ Aut(A).记Γm(n)=A(×)〈α〉,则它是一个2元生成的多重循环群.本文给出了 Γm(n)的准确的剩余有限性质.