The Ultraconvergence of Eigenvalues for Bi-Quadratic Finite Elements

Abstract

The classical eigenvalue problem of the second-order elliptic operator is approximated with bi-quadratic finite element in this paper. We construct a new superconvergent function recovery operator, from which the $O(h^8|\ln h|^2)$ ultraconvergence of eigenvalue approximation is obtained. Numerical experiments verify the theoretical results.