Local Convergence of Adaptive Methods for Nonlinear Partial Differential Equations
Local Convergence of Adaptive Methods for Nonlinear Partial Differential Equations
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发表时间:
2010-01
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通讯作者:
M. Holst;G. Tsogtgerel;Yunrong Zhu
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作者:
M. Holst;G. Tsogtgerel;Yunrong Zhu
In this article we develop convergence theory for a general class of adaptive approximation algorithms for abstract nonlinear operator equations on Banach spaces, and then use the theory to obtain convergence results for practical adaptive finite element methods (AFEM) applied to several classes of nonlinear elliptic equations. In the first part of the paper, we develop a weak-* convergence framework for nonlinear operators, whose Gateaux derivatives are locally Lipschitz and satisfy a local inf-sup condition. The framework can be viewed as extending the recent convergence results for linear problems of Morin, Siebert and Veeser to a general nonlinear setting. We formulate an abstract adaptive approximation algorithm for nonlinear operator equations in Banach spaces with local structure. The weak-* convergence framework is then applied to this class of abstract locally adaptive algorithms, giving a gen eral convergence result. The convergence result is then applied to a standard AFEM algorithm in the case of sev- eral semilinear and quasi-linear scalar elliptic equation s and elliptic systems, including: a semilinear problem with subcritical nonlinearity, the st eady Navier-Stokes equations, and a quasilinear problem with nonlinear diffusion. This yields several new AFEM convergence results for these nonlinear problems. In the second part of the paper we develop a second abstract convergence framework based on strong contraction, extend- ing the recent contraction results for linear problems of Ca scon, Kreuzer, Nochetto, and Siebert and of Mekchay and Nochetto to abstract nonlinear problems. We then establish conditions under which it is possible to apply the contracti on framework to the abstract adaptive algorithm defined earlier, giving a contraction re sult for AFEM-type algorithms applied to nonlinear problems. The contraction result is th en applied to a standard AFEM algorithm in the case of several semilinear scalar elliptic equations, including: a semi- linear problem with subcritical nonlinearity, the Poisson -Boltzmann equation, and the Hamiltonian constraint in general relativity, yielding AF EM contraction results in each case.