The nuclear matter equation of state with consistent two- and three-body perturbative chiral interactions

We compute the energy per particle of infinite symmetric nuclear matter from chiral N3LO (next-to-next-to-next-to-leading order) two-body potentials plus N2LO three-body forces. The low-energy constants of the chiral three-nucleon force that cannot be constrained by two-body observables are fitted to reproduce the triton binding energy and the 3H-3He Gamow-Teller transition matrix element. In this way, the saturation properties of nuclear matter are reproduced in a parameter-free approach. The equation of state is computed up to third order in many-body perturbation theory, with special emphasis on the role of the third-order particle-hole diagram. The dependence of these results on the cutoff scale and regulator function is studied. We find that the inclusion of three-nucleon forces consistent with the applied two-nucleon interaction leads to a reduced dependence on the choice of the regulator only for lower values of the cutoff.Comment: 9 pages, 12 figures, 3 tables, to be published in Physical Review C. arXiv admin note: text overlap with arXiv:1209.553

Chiral nucleon-nucleon forces in nuclear structure calculations

Realistic nuclear potentials, derived within chiral perturbation theory, are a major breakthrough in modern nuclear structure theory, since they provide a direct link between nuclear physics and its underlying theory, namely the QCD. As a matter of fact, chiral potentials are tailored on the low-energy regime of nuclear structure physics, and chiral perturbation theory provides on the same footing two-nucleon forces as well as many-body ones. This feature fits well with modern advances in ab-initio methods and realistic shell-model. Here, we will review recent nuclear structure calculations, based on realistic chiral potentials, for both finite nuclei and infinite nuclear matter.Comment: 10 pages, 8 figures, plenary talk presented at "Nucleus-Nucleus 2015" Conference, 21-26 June 2015, Catania, to be published in the "Conference Proceedings" Series of the Italian Physical Societ

Study of nucleonic matter with a consistent two- and three-body perturbative chiral interaction

We calculate perturbatively the energy per nucleon in infinite nuclear matter with a chiral N3LO (next-to-next-to-next-to-leading order) two-body potential plus a N2LO three-body force (3BF). The 3BF low-energy constants which cannot be constrained by two-body observables are chosen such as to reproduce the A=3 binding energies and the triton Gamow-Teller matrix element. This enables to study the nuclear matter equation of state in a parameter-free approach.Comment: 7 pages, 5 figures, talk presented at "XIV Convegno su Problemi di Fisica Nucleare Teorica", Cortona October 29-31, 2013. Submitted to Journal of Physics: Conferences Serie

How well does the chiral expansion converge in nuclear and neutron matter

The equations of state of nuclear and neutron matter (and, more generally, neutron-rich matter) play a fundamental role towards the understanding of a broad spectrum of systems, ranging from the skins of neutron-rich nuclei to the structure of compact stars. After a brief review of different approaches to predict the properties of nuclear and neutron matter, we will focus on error quantification in effective field theory. The various sources of uncertainty and their impact in infinite matter will be explored. We will then report on recent calculations of the nuclear and neutron matter equations of state at different orders of the chiral expansion as well as changing resolution scale. We will discuss the significance of such predictions as a foundation for future studies of convergence of the chiral perturbation series

Towards order-by-order calculations of the nuclear and neutron matter equations of state in chiral effective field theory

We calculate the nuclear and neutron matter equations of state from microscopic nuclear forces at different orders in chiral effective field theory and with varying momentum-space cutoff scales. We focus attention on how the order-by-order convergence depends on the choice of resolution scale and the implications for theoretical uncertainty estimates on the isospin asymmetry energy. Specifically we study the equations of state using consistent NLO and N2LO (next-to-next-to-leading order) chiral potentials where the low-energy constants cD and cE associated with contact vertices in the N2LO chiral three-nucleon force are fitted to reproduce the binding energies of 3H and 3He as well as the beta-decay lifetime of 3H. At these low orders in the chiral expansion there is little sign of convergence, while an exploratory study employing the N3LO two-nucleon force together with the N2LO three-nucleon force give first indications for (slow) convergence with low-cutoff potentials and poor convergence with higher-cutoff potentials. The consistent NLO and N2LO potentials described in the present work provide the basis for estimating theoretical uncertainties associated with the order-by-order convergence of nuclear many-body calculations in chiral effective field theory.Comment: 9 pages, 6 figures. Accepted for publication in Physical Review

On the current circulation about a high-voltage s/c: Two more case-studies by the TSS-1R tethered satellite mission

Magnetic field observations by the TEMAG experiment on the TSS-1R satellite for two events of constant stimulated current along the tether are discussed. Previous evidence of a complex, unexpected, electric azimuthal current circulation in close proximity of the high-voltage spacecraft is further supported and complemented. While previous events cover time intervals shorter than a spin cycle, the two new ones allow a complete coverage for a full spin cycle. The need of deeper theoretical approach as well as of more experimental observations is stressed