  Regulator functions applied to two- and three-nucleon forces are a necessary
ingredient in many-body calculations based on chiral effective field theory
interactions. These interactions have been developed recently with a variety of
different cutoff forms, including regulating both the momentum transfer (local)
and the relative momentum (nonlocal). While in principle any regulator that
suppresses high momentum modes can be employed, in practice artifacts are
inevitable in current power counting schemes. Artifacts from particular
regulators may cause significant distortions of the physics or may affect
many-body convergence rates, so understanding their nature is important. Here
we characterize the differences between cutoff effects using uniform matter at
Hartree-Fock and second-order in the interaction as a testbed. This provides a
clean laboratory to isolate phase-space effects of various regulators on both
two- and three-nucleon interactions. We test the normal-ordering approximation
for three-nucleon forces in nuclear matter and find that the relative size of
the residual 3N contributions is sensitive to the employed regularization
scheme.
