  Within a scalar model theory of gravity, where the interaction between
particles is given by the half-retarded + half-advanced solution of the scalar
wave equation, we consider an N-body problem: we investigate configurations of
N particles which form an equilateral N-angle and are in helical motion about
their common center. We prove that there exists a unique equilibrium
configuration and compute the equilibrium radius explicitly in a post-Newtonian
expansion.
