Switching boundary conditions in the many-body diffusion algorithm

In this paper we show how the transposition, the basic operation of the per mutation group, can be taken into account in a diffusion process of identic al particles. Whereas in an earlier approach the method was applied to syst ems in which the potential is invariant under interchanging the Cartesian c omponents of the particle coordinates, this condition on the potential is a voided here. In general, the potential introduces a switching of the bounda ry conditions of the walkers. These transitions modelled by a continuous-ti me Markov chain generate sample paths for the propagator as a Feynman-Kac f unctional. A few examples, including harmonic fermions with an anharmonic i nteraction, and the ground-state energy of ortho-helium are studied to eluc idate the theoretical discussion and to illustrate the feasibility of a sig n-problem-free implementation scheme for the recently developed many-body d iffusion approach.