Quantum Monte Carlo Calculations in Nuclear Theory

To a remarkable extent, atomic nuclei can be described as collections of point-like particles whose dynamics are dictated by a nonrelativistic Hamiltonian involving two- and three-nucleon potentials.Ab initio approaches are aimed at solving the many-body Schrödinger equation associated with the nuclear Hamiltonian, which is a highly non-trivial problem because of the nonperturbative nature and the strong spin-isospin dependence of the nuclear forces. Within this framework it is possible to disentangle the theoretical uncertainty coming from modeling the nuclear potential and currents from that due to the approximations that are usually inherent in many-body techniques.Our many-body method of choice is quantum Monte Carlo (QMC), in particular Green's function Monte Carlo (GFMC), which allows solving the nuclear Schrodinger equation with the required 1% accuracy level for both the ground- and the low-lying excited states of A ≤ 12 (A is the number of nucleons) nuclei. Since 2000 we have been achieving excellent agreement with experiment for nuclei with increasing number of nucleons by using the Argonne V18 two-nucleon interaction and the Illinois three-nucleon interactions (AV18+IL7). During this period many other groups have been developing chiral effective field theory (χEFT) potentials; these are generally nonlocal and notsuitable for QMC methods. We and collaborators have recently developed a local χEFT potential including the Δ-isobar degrees of freedom which can be used with QMC.