  Selfdual variational principles are introduced in order to construct
solutions for Hamiltonian and other dynamical systems which satisfy a variety
of linear and nonlinear boundary conditions including many of the standard
ones. These principles lead to new variational proofs of the existence of
parabolic flows with prescribed initial conditions, as well as periodic,
anti-periodic and skew-periodic orbits of Hamiltonian systems. They are based
on the theory of anti-selfdual Lagrangians introduced and developed recently in
[3], [4] and [5].
