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Compactness method in the finite element theory of nonlinear elliptic problems. (English) Zbl 0642.65075
The authors study finite element approximation of nonlinear elliptic boundary value problems of the type $-\text{div} a(\cdot,u,\text{grad} u)+b(\cdot,u,\text{grad} u)=f \text{ in } \Omega,\quad u=q_ D\text{ auf } \Gamma_ D$ $$a(\cdot,u,\text{grad} u)\cdot n=q_ N$$ auf $$\Gamma_ N=\partial \Omega \setminus \Gamma_ D$$ in a bounded nonpolygonal domain $$\Omega\subset {\mathfrak R}^ 2.$$ The corresponding form $$a(u,v)$$ is assumed to be Lipschitz-continuous and pseudo-monotone (generalized condition S); this guarantees compactness.
In the discretization the domain $$\Omega$$ is approximated by polygonal domains; linear conforming triangular elements are used; the integrals are evaluated by numerical quadratures. Solvability of the discrete problems and convergence to an exact weak solution $$u\in H^ 1(\Omega)$$ are proved. No additional assumption on the regularity of the exact weak solution is needed.
Reviewer: J.Weisel

##### MSC:
 65N30 Finite element, Rayleigh-Ritz and Galerkin methods for boundary value problems involving PDEs 35J65 Nonlinear boundary value problems for linear elliptic equations
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##### References:
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