Strange hadronic matter in a modified quark-meson coupling model

Strange hadronic matter with nucleons, Λ-hyperons and Ξ-hyperons is studied by using a modified quark-meson coupling (MQMC) model in a mean-field approximation. The density dependence of the effective baryon masses as well as the saturation properties and stabilities of the strange hadronic matter are discussed.     

Bulk viscosity of strange quark matter in density dependent quark mass model

We have studied the bulk viscosity of strange quark matter in the density dependent quark mass model (DDQM) and compared results with calculations done earlier in the MIT bag model where u, d masses were neglected and first order interactions were taken into account. We find that at low temperatures and high relative perturbations, the bulk viscosity is higher by 2 to 3 orders of magnitude while at low perturbations the enhancement is by 1–2 order of magnitude as compared to earlier results. Also the damping time is 2–3 orders of magnitude lower implying that the star reaches stability much earlier than in MIT bag model calculations.     

Magnetized strange quark matter in a mass-density-dependent model

We investigate the properties of strange quark matter (SQM) in a strong magnetic field with quark confinement by the density dependence of quark masses considering the total baryon number conservation, charge neutrality and chemical equilibrium. It is found that an additional term should appear in the pressure expression to maintain thermodynamic consistency. At fixed density, the energy density of magnetized SQM varies with the magnetic field strength. By increasing the field strength an energy minimum exists located at about 6×10¹⁹ Gauss when the density is fixed at two times the normal nuclear saturation density.     

Magnetic catalysis of stability of quark matter in the Nambu-Jona-Lasinio model

The effect of an external magnetic field H on the stability of quark matter is studied on the basis of the Nambu-Jona-Lasinio model. It is shown that, at H = 0, droplets of quark matter are stable only in the case where the coupling constant G is greater than some value G_bag. If H ≠ 0, stable multiquark formations may exist even for G ≤ G_bag (magnetic catalysis of stability). For G > G_bag, a magnetic field facilitates the formation of stable quark matter.     

Strange solitons in a chiral quark-meson model

We consider aSU(3) quark soliton model based on chiral invariant quark-meson coupling. We find soliton solutions with nonzero strangeness andB=1 in the model with nontrivial kaonic fields, for values of the coupling constant greater than the phenomenologically acceptable number. Hence they do not correspond to known strange baryons.     

Superconductivity in quark matter

Superconductivity due to the pairing of relativistic quarks in ultra-dense matter is discussed. Ginzburg-Landau equations are derived, and the possibility of an Abrikosov vortex phase is considered.     

Transversity decomposition of quark angular momentum

We express the correlation between quark transversity and (total) quark angular momentum in terms of the second moment of chirally odd generalized parton distributions. The resulting relation allows to determine how much quarks of a given transversity contribute to the total angular momentum of the nucleon.     

The nucleon-delta splitting in the chiral quark-meson model

Cranking techniques are employed to calculate the N − Δ splitting in the chiral quark-meson model. A splitting of 322 MeV is obtained. It is determined that about 80% of the angular momentum and isospin in the model are carried by the mesons.     

Thermodynamical information on quark matter from the nucleon valence quark distribution

If the valence quarks in the nucleon are considered as a gas of the non-interacting massless particles, an expression of the xF₃(x) structure function is obtained which reproduces very well the experimental $\text{v(}\text{v}\text{)}$N data in the range 0.1?x?0.8. The effective temperature of such a quark gas is found to be of the order of 50 MeV.     

Faces of quark matter

Based on an analysis in the framework of a coalescence hadronization model (ALCOR) we conclude that in heavy ion collisions at CERN SPS and RHIC energies a new type of matter, the massive quark-antiquark matter is produced.     

Quark-clustering in cold quark matter

Quarks are proposed to be grouped together to make quark-clusters due to the strong interaction in cold quark matter at a few nuclear densities,because a weakly coupling treatment of the interaction between quarks there would be inadequate.Cold quark matter is then conjectured to be in solid state （i.e.,forming a crystal structure） if the inter-cluster potential is deep enough to localize clusters in lattice.Such a solid state of cold quark matter would be very necessary for us to understand different manifestations of pulsar-like compact stars,and could not be ruled by first principles.     

Superfluidity in ultra-relativistic quark matter

Possible forms of superfluid order parameter are discussed for quark matter at densities where the Fermi energy is much greater than the mass of the quarks. Ginzburg-Landau equations for the order parameter are derived and solved.     

Supercurrents in color-superconducting quark matter

We review the basic properties of the currCFL-K⁰ phase in dense quark matter. At asymptotically large densities, three-flavor quark matter is in the color-flavor locked (CFL) state. The currCFL-K⁰ state is a way to respond to “stress” on the quark Cooper pairing, imposed at more moderate densities by the strange quark mass and the conditions of electric and color neutrality. We show how a kaon supercurrent is incorporated in a purely fermionic formalism, and show that the net current vanishes due to cancellation of fermion and charge-conjugate fermion contributions.     

Quark-clustering in cold quark matter

Quarks are proposed to be grouped together to make quark-clusters due to the strong interaction in cold quark matter at a few nuclear densities, because a weakly coupling treatment of the interaction between quarks there would be inadequate. Cold quark matter is then conjectured to be in solid state (i.e., forming a crystal structure) if the inter-cluster potential is deep enough to localize clusters in lattice. Such a solid state of cold quark matter would be very necessary for us to understand different manifestations of pulsar-like compact stars, and could not be ruled by first principles.     

Color superconductivity in quark matter

Selected problems related to color superconductivity are discussed in a rather elementary way. The text was submitted by the author in English.     

Self-consistently thermodynamic treatment for strange quark matter in the effective mass bag model

In the framework of the effective mass bag model (EMBM) we have performed the thermodynamical treatment for strange quark matter (SQM) self-consistently, which overcomes the inconsistencies in the thermodynamical properties of the system. Because of the existence of the pressure extra term, the SQM equation of state (EOS) becomes stiffer comparing with the one for the original EMBM. It is interesting to find that in our treatment the SQM EOS is almost independent of the strong coupling constant g . In this case the SQM EOS seems to get back to the EOS for the original MIT bag model. However, this treatment still has influence on the EOS for hybrid star matter and the corresponding mass-radius relations. With the increase of the strong coupling constant g , the EOS for hybrid star matter gets obviously stiff. From our treatment we notice that the pressure extra term can make a hybrid star more compact than the one described in the original EMBM and this model is more suitable to describe the hybrid stars with small radii.