Abstract
The nucleon-nucleon interaction is an important requirement for investigations of nuclear structure and reactions, as well as for astrophysical models such as r-process nucleosynthesis and neutron stars. The traditional approach to low-energy nuclear physics is to treat nucleons as immutable objects interacting via phenomenological forces. The use of phenomenological interactions, rather than one derived from a microscopic theory, raises questions as to the reliability of predictions for exotic regions of the nuclear chart. The quark-meson coupling (QMC) model uses a relativistic mean-field approach to provide a microscopically derived nucleon-nucleon interaction, which takes into account the quark structure of the nucleon.The Skyrme energy density functional is a popular phenomenological tool in studies of nuclear structure and reactions. In this work, the QMC density functional was used to produce a set of Skyrme parameterisations, in the hopes that they will give more reliable predictions for exotic nuclei. In conjunction with Hartree-Fock-Bogoliubov (HFB) calculations, the Skyrme-QMC (SQMC) parameterisations have been used to model the ground-state properties of individual nuclei and nucleus-nucleus potentials for Ca + Sn reactions. The SQMC parameterisation performs with an accuracy comparable to modern phenomenological functionals. From this, one can investigate the importance of the isovector terms of the nucleon-nucleon interaction, which are particularly significant for exotic, neutron-rich regions of the nuclear chart.One of the notable successes of the QMC model is its derivation of nuclear spin-orbit coupling. The isovector dependence of the spin-orbit equation of state is remarkably similar to that of the modern UNEDF1 phenomenological density functional. HFB calculations along the Sn isotopic chain reveal that the isovector properties of the spin-orbit term impact binding energies to a level that will be significant for astrophysical r-process modelling.
Highlights
The behaviour of exotic nuclear systems is an important question for nuclear, particle and astrophysics
The quark-meson coupling (QMC) model is a relativistic mean-field approach which self-consistently accounts for the in-medium modification of the quark structure of bound nucleons
The ω and ρ meson fields can be identified with real particles and their experimental masses used. This leaves only four free parameters in the QMC model, Gσ, Gω, Gρ and the σ meson mass, all of which are fixed by the central terms of the functional
Summary
The behaviour of exotic nuclear systems is an important question for nuclear, particle and astrophysics. The quark-meson coupling (QMC) model is a relativistic mean-field approach which self-consistently accounts for the in-medium modification of the quark structure of bound nucleons. [3,4,5], it confines three quarks to a nucleon bag and allows the quarks of different bags to interact by exchanging σ, ω and ρ mesons. This results in an energy density functional with only four free parameters (a coupling constant for each meson field and the mass of the σ meson). The model derives nuclear spin-orbit coupling, a relativistic effect essential for shell structure of nuclei and dissipation in collisions
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