Nuclear matter properties from local chiral interactions with $\Delta$ isobar intermediate states

TL;DR

This paper presents new nuclear matter calculations using local chiral interactions with explicit $elta$ isobar states, achieving good saturation properties and agreement with empirical data, advancing microscopic nuclear modeling.

Contribution

It introduces the first nuclear matter calculations with a fully local N3LO$elta$ chiral interaction, demonstrating improved saturation and empirical agreement.

Findings

Successful saturation point for symmetric nuclear matter

Good agreement with empirical symmetry energy constraints

Explicit $elta$ isobars reduce the needed three-nucleon interaction strength

Abstract

Using two-nucleon and three-nucleon interactions derived in the framework of chiral perturbation theory (ChPT) with and without the explicit $\Delta$ isobar contributions, we calculate the energy per particle of symmetric nuclear matter and pure neutron matter in the framework of the microscopic Brueckner-Hartree-Fock approach. In particular, we present for the first time nuclear matter calculations using the new fully local in coordinate-space two-nucleon interaction at the next-to-next-to-next-to-leading-order (N3LO) of ChPT with $\Delta$ isobar intermediate states (N3LO$\Delta$) recently developed by Piarulli et al. [arXiv:1606:06335]. We find that using this N3LO$\Delta$ potential, supplemented with a local N2LO three-nucleon interaction with explicit $\Delta$ isobar degrees of freedom, it is possible to obtain a satisfactory saturation point of symmetric nuclear matter. For this combination of two- and three-nucleon interactions we also calculate the nuclear symmetry energy and we compare our results with the empirical constraints on this quantity obtained using the excitation energies to isobaric analog states in nuclei and using experimental data on the neutron skin thickness of heavy nuclei, finding a very good agreement with these empirical constraints in all the considered nucleonic density range. In addition, we find that the explicit inclusion of $\Delta$ isobars diminishes the strength of the three-nucleon interactions needed the get a good saturation point of symmetric nuclear matter. We also compare the results of our calculations with those obtained by other research groups using chiral nuclear interactions with different many-body methods, finding in many cases a very satisfactory agreement.