Multigrid methods applied to standard linear finite element discretizations of linear elliptic boundary value problems in two dimensions,are considered. In the multigrid method, damped Jacobi or damped Gauss-Seidel is...
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Multigrid methods applied to standard linear finite element discretizations of linear elliptic boundary value problems in two dimensions,are considered. In the multigrid method, damped Jacobi or damped Gauss-Seidel is used as a smoother. It is proven that the two-grid method with nu pre-smoothing iterations has a contraction number with respect to the maximum norm that is (asymptotically) bounded by Cnu-1/2 \ln h(k)\2, with h(k);a suitable mesh size parameter, Moreover, it is shown that this bound is sharp in the sense that a factor \ln h(k)\ is necessary.
The diffuse domain method for partial differential equations on complicated geometries recently received strong attention in particular from practitioners, but many fundamental issues in the analysis are still widely ...
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The diffuse domain method for partial differential equations on complicated geometries recently received strong attention in particular from practitioners, but many fundamental issues in the analysis are still widely open. In this paper, we study the diffuse domain method for approximating second order elliptic boundary value problems posed on bounded domains and show convergence and rates of the approximations generated by the diffuse domain method to the solution of the original second order problem when complemented by Robin, Dirichlet or Neumann conditions. The main idea of the diffuse domain method is to relax these boundary conditions by introducing a family of phase-field functions such that the variational integrals of the original problem are replaced by a weighted average of integrals of perturbed domains. From a functional analytic point of view, the phase-field functions naturally lead to weighted Sobolev spaces for which we present trace and embedding results as well as various types of Poincar, inequalities with constants independent of the domain perturbations. Our convergence analysis is carried out in such spaces as well, but allows to draw conclusions also about unweighted norms applied to restrictions on the original domain. Our convergence results are supported by numerical examples.
In this paper, we prove that if Q is a positive continuous function in R(N) and satisfies the suitable conditions, then for sufficiently small lambda > 0, -Delta u + u = Q(z)u(p-1) with the boundary condition u(x, ...
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In this paper, we prove that if Q is a positive continuous function in R(N) and satisfies the suitable conditions, then for sufficiently small lambda > 0, -Delta u + u = Q(z)u(p-1) with the boundary condition u(x, z(N)) = lambda g(x) admits at least three positive solutions in R(+)(N). (C) 2011 Elsevier Ltd. All rights reserved.
For some boundaryvalueproblems for equations of the form $\nabla ^2 u + f(x,u,\nabla u) = 0$ with linear boundary conditions we give a convergence analysis for a quasi-Newton method that converges superlinearly in t...
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For some boundaryvalueproblems for equations of the form $\nabla ^2 u + f(x,u,\nabla u) = 0$ with linear boundary conditions we give a convergence analysis for a quasi-Newton method that converges superlinearly in the $C^1 $ norm. This scheme for infinite-dimensional problems becomes a method for the finite-dimensional problems that are produced by discretizing the differential equation. This method is a generalization of a method proposed by Hart and Soul for discretizations of two point boundaryvalueproblems.
In this paper we study the existence of infinitely many solutions for a class of elliptic boundary value problems. The existence results include both superlinear case and an asymptotically linear case. Our arguments a...
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In this paper we study the existence of infinitely many solutions for a class of elliptic boundary value problems. The existence results include both superlinear case and an asymptotically linear case. Our arguments are based on a recently given new Fountain Theorem due to Zou [W. Zou, Variant Fountain Theorems and their applications, Manuscripta Math. 104 (2001) 343-358]. (c) 2009 Elsevier Ltd. All rights reserved.
In this paper, we present convergence rates for solving elliptic boundary value problems with singular parameterizations in isogeometric analysis. First, the approximation errors with the L-2(Omega)-norm and the H-1(O...
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In this paper, we present convergence rates for solving elliptic boundary value problems with singular parameterizations in isogeometric analysis. First, the approximation errors with the L-2(Omega)-norm and the H-1(Omega)-seminorm are estimated locally. The impact of singularities is considered in this framework. Second, the convergence rates for solving PDEs with singular parameterizations are discussed. These results are based on a weak solution space that contains all of the weak solutions of elliptic boundary value problems with smooth coefficients. For the smooth weak solutions obtained by isogeometric analysis with singular parameterizations and the finite element method, both are shown to have the optimal convergence rates. For non-smooth weak solutions, the optimal convergence rates are reached by setting proper singularities of a controllable parameterization, even though convergence rates are not optimal by finite element method, and the convergence rates by isogeometric analysis with singular parameterizations are better than the ones by the finite element method. (C) 2017 Elsevier B.V. All rights reserved.
Existence, uniqueness, and optimal order H-2, H-1, and L-2 error bounds are established for the orthogonal spline collocation solution of a Dirichlet boundaryvalue problem on the unit square. The linear, elliptic, no...
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Existence, uniqueness, and optimal order H-2, H-1, and L-2 error bounds are established for the orthogonal spline collocation solution of a Dirichlet boundaryvalue problem on the unit square. The linear, elliptic, nonself-adjoint, partial differential equation is given in nondivergence form. The approximate solution, which is a tensor product of continuously differentiable piecewise polynomials of degree r greater than or equal to 3, is determined by satisfying the partial differential equation at the nodes of a composite Gauss quadrature.
This paper is concerned with the regularity of the solutions to elliptic boundary value problems in polygonal domains Omega contained in R-2. Especially, we consider the specific scale B-tau(alpha)(L-tau(Omega)), 1/ta...
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This paper is concerned with the regularity of the solutions to elliptic boundary value problems in polygonal domains Omega contained in R-2. Especially, we consider the specific scale B-tau(alpha)(L-tau(Omega)), 1/tau = alpha/2 + 1/p, of Besov spaces. The regularity of the variational solution in these Besov spaces determines the order of approximation that can be achieved by adaptive and nonlinear numerical schemes. The proofs are based on specific representations of the solutions which were, e.g., derived by Grisvard [1], and on characterizations of Besov spaces by wavelet expansions. (C) 1999 Elsevier Science Ltd. All rights reserved.
The singularities near the crack tips of homogeneous materials are monotone of type r(alpha) and r(alpha)log(delta)r, (depending on the boundary conditions along nonsmooth domains). However. the singularities around t...
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The singularities near the crack tips of homogeneous materials are monotone of type r(alpha) and r(alpha)log(delta)r, (depending on the boundary conditions along nonsmooth domains). However. the singularities around the interfacial cracks of the heterogeneous bimaterials are oscillatory of type, r(alpha) sin(epsilon logr). The method of auxiliary mapping (MAM). introduced by Babuska and Oh, was proven to be successful in dealing with, r(alpha) type singularities. However, the effectiveness of MAM is reduced in handling oscillating singularities. This paper deals with oscillating singularities as well as the monotone singularities by extending MAM through introducing the power auxiliary mapping and the exponential auxiliary mapping. (C) 2001 Academic Press.
Fully diagonalized spectral methods using Sobolev orthogonal/biorthogonal basis functions are proposed for solving second order elliptic boundary value problems. We first construct the Fourier-like Sobolev polynomials...
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Fully diagonalized spectral methods using Sobolev orthogonal/biorthogonal basis functions are proposed for solving second order elliptic boundary value problems. We first construct the Fourier-like Sobolev polynomials which are mutually orthogonal (resp. bi-orthogonal) with respect to the bilinear form of the symmetric (resp. unsymmetric) elliptic Neumann boundaryvalueproblems. The exact and approximation solutions are then expanded in an infinite and truncated series in the Sobolev orthogonal polynomials, respectively. An identity is also established for the a posterior error estimate with a simple error indicator. Further, the Fourier-like Sobolev orthogonal polynomials and the corresponding Legendre spectral method are proposed in parallel for Dirichlet boundaryvalueproblems. Numerical experiments illustrate that our Legendre methods proposed are not only efficient for solving ellipticproblems but also equally applicable to indefinite Helmholtz equations and singular perturbation problems. (C) 2018 IMACS. Published by Elsevier B.V. All rights reserved.
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