The Extrapolation Of The Eigenvalue Problem Using Q₁～(rot) Element

In this paper, we expand the eigenvalue of Poisson equation using nonconforrn-ing Q1rot element. The principal term of error we get is not negative. In general, the approximate eigenvalue is the upper bound, but the approximate eigenvalue may be the lower bound when the principal term is zero. We also extrapolate the expansion arid enhance the accuracy of the eigenvalue from the second order to the fourth order. Finally, we suggest an algorithm and compute the approximate eigenvalue of Poisson equation in square and L-shape domains, then we analyse the approximate eigenvalue.