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We present quantum Monte Carlo calculations of light nuclei, neutron-α scattering, and neutron matter using local two-and three-nucleon (3N) interactions derived from chiral effective field theory up to next-to-next-to-leading order (N 2 LO). The two undetermined 3N low-energy couplings are fit to the 4 He binding energy and, for the first time, to the spin-orbit splitting in the neutron-α P -wave phase shifts. Furthermore, we investigate different choices of local 3N-operator structures and find that chiral interactions at N 2 LO are able to simultaneously reproduce the properties of A = 3, 4, 5 systems and of neutron matter, in contrast to commonly used phenomenological 3N interactions.Three-nucleon (3N) interactions are essential for a reliable prediction of the properties of light nuclei and nucleonic matter [1][2][3][4][5]. In quantum Monte Carlo (QMC) calculations phenomenological 3N interactions such as the Urbana [6] and Illinois [7] models have been used with great success [3,8]. However, such models suffer from certain disadvantages: They are not based on a systematic expansion and it was found that the Illinois forces tend to overbind neutron matter [9,10]. It is therefore unlikely that these phenomenological models can be used to correctly predict the properties of heavy neutron-rich nuclei.An approach which addresses these shortcomings is chiral effective field theory (EFT) [2,[11][12][13][14]. Chiral EFT is a low-energy effective theory consistent with the symmetries of quantum chromodynamics and provides a systematic expansion for nuclear forces. It includes contributions from long-range pion-exchange interactions explicitly and expands the short-distance interactions into a systematic set of contact operators accompanied by low-energy couplings fit to experimental data. Chiral EFT enables the determination of theoretical uncertainties and systematic order-by-order improvement; for recent work see Refs. [15][16][17][18].Chiral EFT also predicts consistent many-body interactions. In Weinberg power counting, 3N forces first enter at next-to-next-to-leading order (N 2 LO) [19,20] and contain three contributions: A two-pion-exchange interaction V C , a one-pion-exchange-contact interaction V D , and a 3N contact interaction V E . While the first is accompanied by the couplings c i from the pion-nucleon sector, the latter two are accompanied by the couplings c D and c E , which have to be determined in A > 2 systems.In addition to systematic nuclear forces, reliable manybody methods are required to describe properties of light nuclei and of dense neutron matter. QMC approaches, which solve the many-body Schrödinger equation stochastically, are such a class of methods. Both the Green's function Monte Carlo (GFMC) method and the auxiliary-field diffusion Monte Carlo (AFDMC) method rely on projection in imaginary time τ ,with H the Hamiltonian of the system and |Ψ T a trial wave function not orthogonal to the many-body ground state |Ψ 0 . For a recent review of developments and applications of QMC methods...

Quantum Monte Carlo methods have recently been employed to study properties of nuclei and infinite matter using local chiral effective field theory interactions. In this work, we present a detailed description of the auxiliary field diffusion Monte Carlo algorithm for nuclei in combination with local chiral two-and three-nucleon interactions up to next-to-next-to-leading order. We show results for the binding energy, charge radius, charge form factor, and Coulomb sum rule in nuclei with 3 ≤ A ≤ 16. Particular attention is devoted to the effect of different operator structures in the three-body force for different cutoffs. The outcomes suggest that local chiral interactions fit to few-body observables give a very good description of the ground-state properties of nuclei up to 16 O, with the exception of one fit for the softer cutoff which predicts overbinding in larger nuclei. arXiv:1802.08932v1 [nucl-th]

Local chiral effective field theory interactions have recently been developed and used in the context of quantum Monte Carlo few-and many-body methods for nuclear physics. In this work, we go over detailed features of local chiral nucleon-nucleon interactions and examine their effect on properties of the deuteron, paying special attention to the perturbativeness of the expansion. We then turn to three-nucleon interactions, focusing on operator ambiguities and their interplay with regulator effects. We then discuss the nuclear Green's function Monte Carlo method, going over both wave-function correlations and approximations for the two-and three-body propagators. Following this, we present a range of results on light nuclei: Binding energies and distribution functions are contrasted and compared, starting from several different microscopic interactions.