Lumped mass error estimates for an isoparametric finite element eigenvalue problem

The error estimate for eigenfunctions and eigenvalues of the second order elliptic operator is analyzed and justified for a class of curved isoparametric triangular finite elements. The quadrature formula giving the lump of the mass matrix is considered. The use of the same nodes for an isoparametric triangle finite element of more than one degree and a quadrature formula is the phenomenon investigated in the paper. At the end of the paper, the numerical results are presented.