We report the first use of the effective quark-meson coupling (QMC) energy density functional (EDF), derived from a quark model of hadron structure, to study a broad range of ground state properties ...of even-even nuclei across the periodic table in the nonrelativistic Hartree-Fock+BCS framework. The novelty of the QMC model is that the nuclear medium effects are treated through modification of the internal structure of the nucleon. The density dependence is microscopically derived and the spin-orbit term arises naturally. The QMC EDF depends on a single set of four adjustable parameters having a clear physics basis. When applied to diverse ground state data the QMC EDF already produces, in its present simple form, overall agreement with experiment of a quality comparable to a representative Skyrme EDF. There exist, however, multiple Skyrme parameter sets, frequently tailored to describe selected nuclear phenomena. The QMC EDF set of fewer parameters, derived in this work, is not open to such variation, chosen set being applied, without adjustment, to both the properties of finite nuclei and nuclear matter.
ABSTRACT
We report a new equation of state (EoS) of cold and hot hyperonic matter constructed in the framework of the quark–meson-coupling (QMC-A) model. The QMC-A EoS yields results compatible with ...available nuclear physics constraints and astrophysical observations. It covers the range of temperatures from T = 0 to 100 MeV, entropies per particle S/A between 0 and 6, lepton fractions from YL = 0.0 to 0.6, and baryon number densities nB = 0.05–1.2 fm−3. Applications of the QMC-A EoS are made to cold neutron stars (NSs) and to hot proto-neutron stars (PNSs) in two scenarios: (i) lepton-rich matter with trapped neutrinos (PNS-I) and (ii) deleptonized chemically equilibrated matter (PNS-II). We find that the QMC-A model predicts hyperons in amounts growing with increasing temperature and density, thus suggesting not only their presence in PNS but also, most likely, in NS merger remnants. The nucleon–hyperon phase transition is studied through the adiabatic index and the speed of sound cs. We observe that the lowering of (cs/c)2 to and below the conformal limit of 1/3 is strongly correlated with the onset of hyperons. Rigid rotation of cold and hot stars, their moments of inertia and Kepler frequencies are also explored. The QMC-A model results are compared with two relativistic models, the chiral mean field model (CMF), and the generalized relativistic density functional (GRDF) with DD2 (nucleon-only) and DD2Y-T (full baryon octet) interactions. Similarities and differences are discussed.
An isovector-scalar meson is incorporated self-consistently into the quark-meson coupling description of nuclear matter, and its most prominent effects on the structure of neutron stars are ...investigated. The recent measurement of GW170817 is used to constrain the strength of the isovector-scalar channel. With the imminent measurements of the neutron star radii in the NICER mission, it is particularly notable that the inclusion of the isovector-scalar force has a significant impact. Indeed, the effect of this interaction on the neutron star radii and masses is larger than the uncertainties introduced by variations in the parameters of symmetric nuclear matter at saturation, namely the density, binding energy per nucleon, and the symmetry energy. In addition, as the analysis of GW170817 has provided constraints on the binary tidal deformability of merging neutron stars, the predictions for this parameter within the quark-meson coupling model are explored, as well as the moment of inertia and the quadrupole moment of slowly rotating neutron stars.
The apparent discrepancy between the Rosenbluth and the polarization transfer methods for the ratio of the electric to magnetic proton form factors can be explained by a two-photon exchange ...correction which does not destroy the linearity of the Rosenbluth plot. Though intrinsically small, of the order of a few percent of the cross section, this correction is accidentally amplified in the case of the Rosenbluth method.
The presence of exotic hadrons, such as hyperons and Δ isobars, in the dense nuclear matter in their cores has been shown to produce important changes in the properties of neutron stars. Within the ...quark-meson coupling model, we show that the many-body forces generated by the change in the internal quark structure of the baryons in the strong scalar mean fields generated in dense nuclear matter prohibit the appearance of Δ isobars.
The Quark–Meson-Coupling model, which self-consistently relates the dynamics of the internal quark structure of a hadron to the relativistic mean fields arising in nuclear matter, provides a natural ...explanation to many open questions in low energy nuclear physics, including the origin of many-body nuclear forces and their saturation, the spin–orbit interaction and properties of hadronic matter at a wide range of densities up to those occurring in the cores of neutron stars. Here we focus on four aspects of the model (i) a full comprehensive survey of the theory, including the latest developments, (ii) extensive application of the model to ground state properties of finite nuclei and hypernuclei, with a discussion of similarities and differences between the QMC and Skyrme energy density functionals, (iii) equilibrium conditions and composition of hadronic matter in cold and warm neutron stars and their comparison with the outcome of relativistic mean-field theories and, (iv) tests of the fundamental idea that hadron structure changes in-medium.
We build upon the remarkable, model independent constraints on the equation of state of dense baryonic matter established recently by Annala et al. 1. Using the quark-meson coupling model, an ...approach to nuclear structure based upon the self-consistent adjustment of hadron structure to the local meson fields, we show that, once hyperons are allowed to appear in dense matter in β-equilibrium, the equation of state is consistent with those constraints. As a result, while one cannot rule out the occurrence of quark matter in the cores of massive neutron stars, the available constraints are also compatible with the presence of hyperons.
A Powerful New Energy Density Functional Thomas, A. W.; Guichon, P. A. M.; Leong, J. ...
Journal of physics. Conference series,
09/2023, Letnik:
2586, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
We describe the most recent energy density functional derived within the quark-meson coupling model. Although fit to the binding energies and charge radii of just seventy magic nuclei, the ...accuracy with which it reproduces nuclear properties across the entire periodic table is outstanding. As well as outlining a number of those results, we present an argument explaining why having a physically motivated model with a small number of parameters is especially desirable as one seeks to make predictions in new regions of
N
and
Z
. As an example we show the predictions for known super-heavy nuclei that were not included in the fit.
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