ABSTRACT
The earliest effective method for computing dus (A) appears to be the bisection method, which was presented in [2] . For any positive number 0:, define the 2n x 2n Hamiltonian matrix
where the superscript H on matrices (and vectors) denotes the com plex conjugate transposed. Then the bisection method is based on the following theorem. Theorem 1 [2] H(o:) defined by (2) has an eigenvalue whose real part is zero if and only if 0: � dus (A) .
