Hrayr H. Matevosyan

Cold Uniform Matter and Neutron Stars in the Quark-Meson-Coupling Model

Abstract A new density dependent effective baryon–baryon interaction has been recently derived from the quark–meson-coupling (QMC) model, offering impressive results in application to finite nuclei and dense baryon matter. This self-consistent, relativistic, quark-level approach is used to construct the Equation of State (EoS) and to calculate key properties of high density matter and cold, slowly rotating neutron stars. The results include predictions for the maximum mass of neutron-star models, together with the corresponding radius and central density, as well the properties of neutron stars with mass of order 1.4  M ⊙ . Some conditions related to the direct URCA process are explored for the QMC EoS and the parameters relevant to slow rotation, namely the moment of inertia and the period of rotation, are investigated. The results of the calculation, which are found to be in good agreement with available observational data, are compared with the predictions of several more traditional EoS. The QMC EoS provides cold neutron-star models with maximum mass in the range 1.9–2.1  M ⊙ , with central density less than 6 times nuclear saturation density ( n 0 = 0.16 fm −3 ) and offers a consistent description of the stellar mass up to this density limit. In contrast with other models, QMC predicts no hyperon contribution at densities lower than 3 n 0 , for matter in β-equilibrium. At higher densities, Ξ − , 0 and Λ hyperons are present, with consequent lowering of the maximum mass. The absence of lighter Σ ± , 0 hyperons is understood as consequence of including the color hyperfine interaction in the response of the quark bag to the nuclear scalar field.

Physical Origin of Density Dependent Force of the Skyrme Type within the Quark Meson Coupling Model

Abstract A density dependent, effective nucleon–nucleon force of the Skyrme type is derived from the quark–meson coupling model—a self-consistent, relativistic quark level description of nuclear matter. This new formulation requires no assumption that the mean scalar field is small and hence constitutes a significant advance over earlier work. The similarity of the effective interaction to the widely used SkM ∗ force encourages us to apply it to a wide range of nuclear problems, beginning with the binding energies and charge distributions of doubly magic nuclei. Finding acceptable results in this conventional arena, we apply the same effective interaction, within the Hartree–Fock–Bogoliubov approach, to the properties of nuclei far from stability. The resulting two neutron drip lines and shell quenching are quite satisfactory. Finally, we apply the relativistic formulation to the properties of dense nuclear matter in anticipation of future application to the properties of neutron stars.

Transverse-momentum-dependent fragmentation and quark distribution functions from the Nambu-Jona-Lasinio-jet model

Using the model of Nambu and Jona-Lasinio to provide a microscopic description of both the structure of the nucleon and of the quark to hadron elementary fragmentation functions, we investigate the transverse momentum dependence of the unpolarized quark distributions in the nucleon and of the quark to pion and kaon fragmentation functions. The transverse momentum dependence of the fragmentation functions is determined within a Monte Carlo framework, with the notable result that the average

Quark-gluon vertex dressing and meson masses beyond ladder-rainbow truncation

P_\perp^2

Calculating kaon fragmentation functions from the Nambu-Jona-Lasinio jet model

of the produced kaons is significantly larger than that of the pions. We also find that

Monte Carlo Simulations of Hadronic Fragmentation Functions using NJL-Jet Model

has a sizable

Model for QCD ground state with magnetic disorder

z

Monte Carlo simulations of hadronic fragmentation functions using the Nambu-Jona-Lasinio-jet model

dependence, in contrast with the naive Gaussian ansatz for the fragmentation functions. Diquark correlations in the nucleon give rise to a non-trivial flavor dependence in the unpolarized transverse momentum dependent quark distribution functions. The