“…Furthermore, due to the presence of a large null space associated with (1) [8,12], these target eigenvalues are actually located in the interior of the spectrum of (1). The eigenvalue problem (1) can thus be solved by inverse power method [2,11,12,21], various Lanczos [2,40] or Arnoldi method [4]. These methods use shift-and-invert technique to compute interior eigenpairs and the computational cost for solving the corresponding linear systems can be excessive.…”