  Neutron matter is an important many-body system that provides valuable
constraints for the equation of state (EOS) of neutron stars. Neutron-matter
calculations employing chiral effective field theory (EFT) interactions have
been extensively used for this purpose. Among the various many-body methods,
quantum Monte Carlo (QMC) methods stand out due to their nonperturbative nature
and the achievable precision. However, QMC methods require local interactions
as input, which leads to the appearance of stronger regulator artifacts as
compared to non-local interactions. To circumvent this, we employ large-cutoff
interactions derived within chiral EFT (400 MeV $\leq \Lambda_c \leq$ 700 MeV)
for studies of pure neutron matter. These interactions have been adjusted to
nucleon-nucleon scattering phase shifts, the triton binding energy, as well as
the triton beta-decay half life. We find that regulator artifacts significantly
decrease with increasing cutoff, leading to a significant reduction of
uncertainties in the neutron-matter EOS. We discuss implications for the
symmetry energy and demonstrate how our new calculations lead to a reduction in
the theoretical uncertainty of predicted neutron-star radii by up to 30% for
low-mass stars.
