“…Our main motivation to study identity-plus-skew-symmetric preconditioners are linear systems arising in the time discretization of dissipative Hamiltonian differential equations of the form Eż = (J − R) z + f (t), z(t 0 ) = z 0 , whereż denotes the derivative with respect to time, J is a skew-symmetric matrix, R is symmetric positive semidefinite, and E is the symmetric positive semidefinite Hessian of a quadratic energy functional (Hamiltonian) H(z) = 1 2 z T Ez; see, e.g., [2,10,14,20,31,32] for such systems in different physical domains and applications. If one discretizes such ETNA Kent State University and Johann Radon Institute (RICAM) SPARSE SHIFTED SKEW-SYMMETRIZERS AND PRECONDITIONING 371 systems in time, e.g., with the implicit Euler method, and sets z k = z(t k ), then in each time step t k one has to solve a linear system of the form (1.1) (E − h(J − R))z k+1 = Ez k + hf (t k ).…”