  There is no relativistic Hamiltonian for many particles systems except for
free particles and this has been accepted since the 1960s from the work of
Currie, Jordan and Sudarshan, Cannon and Jordan, and Leutwyler. This is the
problem we will address in this paper by coupling relativistic particles with a
scalar field. The Hamiltonian we derive is explicitly relativistic and in the
non-relativistic limit gives a Hamiltonian with two body interaction. However,
we find that the Poincare algebra is still not satisfied because of the
inherent time delayed interaction in relativistic particle systems.
