Neutron matter based on chiral effective field theory interactions

Neutron matter presents a unique system for chiral effective field theory (EFT), because all many-body forces among neutrons are predicted to next-to-next-to-next-to-leading order (N3LO). We present the first complete N3LO calculation of the neutron matter energy. Our results provide constraints for neutron-rich matter in astrophysics with controlled theoretical uncertainties. In addition, we present the first quantum Monte Carlo (QMC) calculations with chiral EFT interactions. We present auxiliary-field diffusion Monte Carlo (AFDMC) calculations for the neutron matter energy up to saturation density based on local chiral interactions. Our results provide nonperturbative benchmarks with theoretical uncertainties. For the softer interactions, perturbative calculations are in excellent agreement with the AFDMC results.