Analysis of a stabilized three-fields domain decomposition method

Summary. In this paper we prove that, for suitable choices of the bilinear form involved in the stabilization procedure, the stabilized three fields domain decomposition method proposed in [8] is stable and convergent uniformly in the number of subdomains and with respect to their sizes under quite general assumptions on the decomposition and on the discretization spaces. The same is proven to hold for the resulting discrete Steklov-Poincaré operator. Received April 4, 2000 / Revised version received January 9, 2001 / Published online June 17, 2002     

Dirichlet Forms and Markov Processes: A Generalized Framework Including Both Elliptic and Parabolic Cases

We extend the framework of classical Dirichlet forms to a class of bilinear forms, called generalized Dirichlet forms, which are the sum of a coercive part and a linear unbounded operator as a perturbation. The class of generalized Dirichlet forms, in particular, includes symmetric and coercive Dirichlet forms (cf. [6], [10]) as well as time dependent Dirichlet forms (cf. [14]) as special cases and also many new examples. Among these are, e.g. transformations of time dependent Dirichlet forms by -excessive functions h (h-transformations), Dirichlet forms with time dependent linear drift and fractional diffusion operators. One of the main results is that we identify an analytic property of these forms which ensures the existence of associated strong Markov processes with nice sample path properties, and give an explicit construction for such processes. This construction extends previous constructions of the processes in the elliptic and the parabolic cases, is, in particular, carried out on general topological state spaces (as in [10]), and is applied to the above examples.     

Prewavelet analysis of the heat equation

Summary. We consider the heat equation in a smooth domain of R with Dirichlet and Neumann boundary conditions. It is solved by using its integral formulation with double-layer potentials, where the unknown , the jump of the solution through the boundary, belongs to an anisotropic Sobolev space. We approximate by the Galerkin method and use a prewavelet basis on , which characterizes the anisotropic space. The use of prewavelets allows to compress the stiffness matrix from to when N is the size of the matrix, and the condition number of the compressed matrix is uniformly bounded as the initial one in the prewavelet basis. Finally we show that the compressed scheme converges as fast as the Galerkin one, even for the Dirichlet problem which does not admit a coercive variational formulation. Received April 16, 1999 / Published online August 2, 2000     

Stabilized mixed methods for the Stokes problem

Summary The solution of the Stokes problem is approximated by three stabilized mixed methods, one due to Hughes, Balestra, and Franca and the other two being variants of this procedure. In each case the bilinear form associated with the saddle-point problem of the standard mixed formulation is modified to become coercive over the finite element space. Error estimates are derived for each procedure.Dedicated to Ivo Babuka on the occasion of his sixtieth birthday     

A Priori and a Posteriori Error Analysis of a Wavelet-Based Stabilization for the Mixed Finite Element Method

We use Galerkin least-squares terms and biorthogonal wavelet bases to develop a new stabilized dual-mixed finite element method for second-order elliptic equations in divergence form with Neumann boundary conditions. The approach introduces the trace of the solution on the boundary as a new unknown that acts also as a Lagrange multiplier. We show that the resulting stabilized dual-mixed variational formulation and the associated discrete scheme defined with Raviart–Thomas spaces are well-posed and derive the usual a priori error estimates and the corresponding rate of convergence. Furthermore, a reliable and efficient residual-based a posteriori error estimator and a reliable and quasi-efficient one are provided.     

Stabilisation par viscosité de sous-maille pour l'approximation de Galerkin des opérateurs linéaires monotones

This paper presents a stabilized Galerkin technique for approximating monotone linear operators in Hilbert spaces. The key idea consists in introducing an approximation space that is broken up into resolved and subgrid scales so that the bilinear form associated with the problem satisfies a uniform inf-sup condition with respect to this decomposition. An optimal Galerkin approximation is obtained by introducing an artificial diffusion on the subgrid scales.     

An integral equation approximation of the mixed problem for the laplacian in R3

An integral representation for the solutions of the interior and exterior homogeneous mixed problems on a regular bounded open set in R ³ is given in terms of a potential of simple layer on the Dirichlet data and of double layer on the Neumann data. A coercive non-symmetric bilinear form is provided. Singular finite elements containing the first terms of the assymptotic expansion of the singularity are built and error estimates for the surface distributions are given.     

平面弹性力学问题的混合元法的泡函数稳定性及其后验误差估计

该文讨论平面弹性力学问题的混合元法的泡函数稳定性,并导出基于简化的稳定化格式的一种先验误差估计和后验误差估计．这种简化的稳定化格式较通常的格式节省自由度．     

二阶椭圆问题的混合有限元法的泡函数稳定性及其后验误差估计

本文讨论二阶椭圆问题的混合有限元逼近的一种泡函数稳定性,并给出其基于简化的稳定化格式的先验误差估计和后验误差估计.该方法较通常的格式(例如,Raviaxt-Thomas方法的同阶格式)节省大量的自由度.     

OPERATOR-VALUED FOURIER MULTIPLIER THEOREMS ON TRIEBEL SPACES

1IntroductionIn a series of recent publications operator-valued Fourier multipliers on vector-valued func-tion spaces were studied(see e.g.[1,2,3,5,6,7,14,16]).They are needed to establish existence anduniqueness as well as regularity of di?erential equat…     

A wavelet-based stabilization of the mixed finite element method with Lagrange multipliers

We present a new stabilized mixed finite element method for second order elliptic equations in divergence form with Neumann boundary conditions. The approach introduces first the trace of the solution on the boundary as a Lagrange multiplier, which yields a corresponding residual term that is expressed in the Sobolev norm of order 1/2 by means of wavelet bases. The stabilization procedure is then completed with the residuals arising from the constitutive and equilibrium equations. We show that the resulting mixed variational formulation and the associated Galerkin scheme are well posed. In addition, we provide a residual-based reliable and efficient a posteriori error estimate.     

Bubble—函数稳定化混合有限元分析

本文针对混合结构抽象问题，基于「９」的非标准稳定化有限元方法的一般框架研究了ｂｕｂｂｌｅ－函数稳定化方法，该逼近代格式使得Ｂａｂｕｓｋａ－Ｂｒｅｚｚｉ条件是不必要的。     

双线性Fourier乘子算子与Morrey空间

In this paper, by establishing a result concerning the mapping properties for bi(sub)linear operators on Morrey spaces, and the weighted estimates with general weights for the bilinear Fourier multiplier, the author establishes some results concerning the behavior on the product of Morrey spaces for bilinear Fourier multiplier operator with associated multiplierσ satisfying certain Sobolev regularity.     

A finite element approximation of the Griffith’s model in fracture mechanics

Summary. The Griffith model for the mechanics of fractures in brittle materials is consider in the weak formulation of SBD spaces. We suggest an approximation, in the sense of –convergence, by a sequence of discrete functionals defined on finite elements spaces over structured and adaptive triangulations. The quasi-static evolution for boundary value problems is also taken into account and some numerical results are shown. Mathematics Subject Classification (2000):65N30     

On the Poincaré Inequality for Infinitely Divisible Measures

We completely characterize the Poincaré inequality for bilinear forms of gradient type defined on L²-spaces w.r.t. infinitely divisible measures m in terms of the canonical measure associated with m. The characterization is based on an elementary algebraic observation concerning certain quadratic forms associated with m and , which is of its own interest (see Lemma 3.4). Examples include canonical Dirichlet forms on configuration spaces and Dirichlet forms associated to continuous state branching processes. As an application, a strong law of large numbers for time-inhomogeneous one-dimensional subordinators is obtained.Mathematics Subject Classifications (2000) 31C25 (60E07, 60G57, 60H07, 60J80).     

The operator-valued Marcinkiewicz multiplier theorem and maximal regularity

Given a closed linear operator on a UMD-space, we characterize maximal regularity of the non-homogeneous problem with periodic boundary conditions in terms of R-boundedness of the resolvent. Here A is not necessarily generator of a -semigroup. As main tool we prove an operator-valued discrete multiplier theorem. We also characterize maximal regularity of the second order problem for periodic, Dirichlet and Neumann boundary conditions. Received: 21 December 2000; in final form: 12 June 2001 / Published online: 1 February 2002     

Cubic Nonlinear Schrödinger Equation on Three Dimensional Balls with Radial Data

We prove wellposedness of the Cauchy problem for the cubic nonlinear Schrödinger equation with Dirichlet boundary conditions and radial data on 3D balls. The main argument is based on a bilinear eigenfunction estimate and the use of X ^{s, b} spaces. The last part presents a first attempt to study the non radial case. We prove bilinear estimates for the linear Schrödinger flow with particular initial data.     

A NEW STABILIZED FINITE ELEMENT METHOD FOR SOLVING THE ADVECTION-DIFFUSION EQUATIONS

1. IntroductionConsider the advection--diffusion equationin a bounded polygonal domain fl c IR2 with the boundary an, where o < K << 1 is thediffusion parameter, rr > 0 is a given positive constant, g(x) is a given vector field representingthe flow with V…     

Spectral Exterior Calculus

A spectral approach to building the exterior calculus in manifold learning problems is developed. The spectral approach is shown to converge to the true exterior calculus in the limit of large data. Simultaneously, the spectral approach decouples the memory requirements from the amount of data points and ambient space dimension. To achieve this, the exterior calculus is reformulated entirely in terms of the eigenvalues and eigenfunctions of the Laplacian operator on functions. The exterior derivatives of these eigenfunctions (and their wedge products) are shown to form a frame (a type of spanning set) for appropriate L² spaces of k -forms, as well as higher-order Sobolev spaces. Formulas are derived to express the Laplace-de Rham operators on forms in terms of the eigenfunctions and eigenvalues of the Laplacian on functions. By representing the Laplace-de Rham operators in this frame, spectral convergence results are obtained via Galerkin approximation techniques. Numerical examples demonstrate accurate recovery of eigenvalues and eigenforms of the Laplace-de Rham operator on 1-forms. The correct Betti numbers are obtained from the kernel of this operator approximated from data sampled on several orientable and non-orientable manifolds, and the eigenforms are visualized via their corresponding vector fields. These vector fields form a natural orthonormal basis for the space of square-integrable vector fields, and are ordered by a Dirichlet energy functional which measures oscillatory behavior. The spectral framework also shows promising results on a non-smooth example (the Lorenz 63 attractor), suggesting that a spectral formulation of exterior calculus may be feasible in spaces with no differentiable structure. © 2020 Wiley Periodicals, Inc.