Nuclear-Matter Equation of State at High Orders from Effective Field theory

Nuclear matter is an ideal environment for testing nuclear interactions with important consequences for physics ranging from finite nuclei to neutron stars. We report on recent advances in many-body perturbation theory for the equation of state of homogeneous nuclear matter based on chiral nucleon-, three-, and four-nucleon interactions. A novel Monte Carlo framework pushes state-of-the-art calculations at zero and finite temperature to high orders in the chiral as well the many-body expansion. This provides important insights into the rate of convergence of both expansions including associated uncertainty estimates, while the underlying diagrams are handled in an efficient way. The efficacy of the new framework furthermore enables to propagate uncertainties from other sources (e.g., fits of low-energy constants) to the equation of state and beyond. As a first step, we explore new chiral interactions up to next-to-next- to-next-to-leading order (N3LO) in neutron and symmetric nuclear matter with focus on reproducing the empirical saturation point. Finally, we show results for the Fermi-momentum expansion of the ground-state energy of a dilute Fermi gas at fourth order and discuss its convergence for spin one-half fermions in comparison with quantum Monte Carlo results.