We discuss the appearance of quark matter in neutron star cores, focusing on the possibility that the recent observation of a very heavy neutron star could constrain free parameters of quark matter ...models. For that, we use the equation of state derived with the field correlator method, extended to the zero temperature limit, whereas for the hadronic phase we use the equation of state obtained within both the nonrelativistic and the relativistic Brueckner-Hartree-Fock many-body theory. We find a strong dependence of the maximum mass both on the value of the qq interaction V sub(1) and on the gluon condensate G sub(2), for which we introduce a dependence on the baryon chemical potential mu sub(B). We find that the maximum masses are consistent with the observational limit for not too small values of V sub(1).
We have derived and solved numerically the Boltzmann-Vlasov transport equations that includes both two-body collisions and the chiral phase transition by mean of NJL-field dynamics. The scope is to ...understand if the field dynamics supply new genuine effects on the build-up of the elliptic flow v sub(2, a measure of the asymmetry in the momentum space, and in particular if it can affect the relation between v) sub(2) and the shear viscosity to entropy ratio eta/s. Solving the transport equation with a constant cross section for the condition of Au+Au collisions at inline imageinline image it is shown a sizable suppression of v sub(2 due to the attractive nature of the field dynamics that generates the constituent mass. However the key result is that if eta/s of the system is kept fixed by an appropriate local renormalization of the cross section the v) sub(2) does not depend on the details of the collisional and/or field dynamics and in particular it is not affected significantly by the chiral phase transition.
Heavy Ion Collisions (HIC) represent a unique tool to probe the in-medium nuclear interaction in regions away from saturation. In this report, we present a selection of new reaction observables in ...dissipative collisions particularly sensitive to the symmetry term of the nuclear Equation of State (Iso-EoS). We will first discuss the Isospin Equilibration Dynamics. At low energies, this manifests via the recently observed Dynamical Dipole Radiation, due to a collective neutron-proton oscillation, with the symmetry term acting as a restoring force. At higher beam energies, Iso-EoS effects will be seen in Imbalance Ratio Measurements, in particular from the correlations with the total kinetic energy loss. For fragmentation reactions in central events, we suggest to look at the coupling between isospin distillation and radial flow. In Neck Fragmentation reactions, important Iso-EoS information can be obtained from the correlation between isospin content and alignment. The high density symmetry term can be probed from isospin effects on heavy ion reactions at relativistic energies (few
A
GeV range). Rather, isospin sensitive observables are proposed from nucleon/cluster emissions, collective flows and meson production. The possibility to shed light on the controversial neutron/proton effective mass splitting in asymmetric matter is also suggested. A large symmetry repulsion at high baryon density will also lead to an “earlier” hadron-deconfinement transition in
n
-rich matter. A suitable treatment of the isovector interaction in the partonic EoS appears very relevant.
Shear viscosity in hybrid stars Jaccarino, D.; Plumari, S.; Greco, V. ...
Physical review. D, Particles, fields, gravitation, and cosmology,
05/2012, Letnik:
85, Številka:
10
Journal Article
A study of the shear viscosity of hadrons and quarks in hybrid stars has been performed in the framework of the microscopic transport theory. The neutron-star structure has been determined employing ...the equation of state from the Brueckner theory with three-body force for the hadron phase, and the equation of state from the MIT bag model for the deconfi ned quark phase. The nucleon-nucleon cross sections in dense matter have been consistently calculated from the Brueckner G matrix, whereas for the quark-quark cross sections the perturbative QCD has been adopted. Despite that the quark contribution to the shear viscosity is quite small at low temperature, the transition to the deconfined phase makes the equation of state much softer with the result that the baryon viscosity turns out to be enhanced instead of reduced in hybrid stars. The damping time scale of r-modes due to the shear viscosity has been evaluated for several stable configurations of a hybrid star and compared with the neutron-star spin-down time scale induced by the emission gravitation radiation from the r-modes. The enhancement of the total viscosity makes the viscosity time scale comparable with the gravitation radiation one at low temperature.
Recent extensive data from the beam energy scan of the STAR collaboration at BNL-RHIC provide the basis for a detailed update for the universal behavior of the strangeness suppression factor gamma_s ...as function of the initial entropy density, as proposed in our recent paper 1. 1 P. Castorina, S. Plumari and H. Satz, Int. J. Mod. Phys. E26 (2017) 1750081 (arXiv:1709.02706)
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