Numerical Verification of Solutions for Nonlinear Elliptic Problems Using anL^∞Residual Method

We consider a numerical enclosure method with guaranteedL^∞error bounds for the solution of nonlinear elliptic problems of second order. By using an a posteriori error estimate for the approximate solution of the problem with a higher orderC⁰-finite element, it is shown that we can obtain the guaranteedL^∞error bounds with high accuracy. A particular emphasis is that our method needs no assumption of the existence of the solution of the original nonlinear equation, but it follows as the result of computation itself. A numerical example that confirms the effectiveness of the method is presented.