Fermion-scalar interactions with domain wall fermions - art. no. 054507

Domain wall fermions are defined on a lattice with an extra direction, the size of which controls the chiral properties of the theory. When gauge fiel ds are coupled to domain wall fermions the extra direction is treated as an internal flavor space. Here it is found that this is not the case for scal er fields. Instead, the interaction takes place only along the link that co nnects the boundaries of the extra direction. This reveals a richness in th e way different spin particles are coupled to domain wall fermions. As an a pplication, 4-fermion models are studied using large N techniques and the r esults are supported by numerical simulations with N = 2. It is found that the chiral properties of domain wall fermions in these models are good acro ss a large range of couplings and that a phase with parity-flavor broken sy mmetry can develop for negative bare masses if the number of sites along th e extra direction is finite.