On Hamiltonian and Symplectic Lanczos Processes

Large sparse Hamiltonian eigenvalue problems arise in a variety of contexts. These problems can be attacked directly, or they can rst be transformed to problems having some related structure, such as symplectic or skew Hamiltonian. In the interest of eciency, stability, and accuracy, such problems should be solved by methods that preserve the structure, whether it be Hamiltonian, skew Hamiltonian, or symplectic