  Treating the fermionic ground state problem as a constrained stochastic
optimization problem, a formalism for fermionic quantum Monte Carlo is
developed that makes no reference to a trial wavefunction. Exchange symmetry is
enforced by nonlocal terms appearing in the Green's function corresponding to a
new kind of walker propagation. Complemented by a treatment of diffusion that
encourages the formation of a stochastic nodal surface, we find that an
approximate long-range extension of walker cancellations can be employed
without introducing significant bias, reducing the number of walkers required
for a stable calculation. A proof-of-concept implementation is shown to give a
stable fermionic ground state for simple harmonic and atomic systems.
