We study the hadron-quark phase transition in the interior of hot protoneutron stars, combining the Brueckner-Hartree-Fock approach for hadronic matter with the MIT bag model or the Dyson-Schwinger model for quark matter. We examine the structure of
the mixed phase constructed according to different prescriptions for the phase transition, and the resulting consequences for stellar properties. We find important effects for the internal composition, but only very small influence on the global stellar properties.
We calculate the structure of neutron star interiors comprising both the hadronic and the quark phases. For the hadronic sector we employ a microscopic equation of state involving nucleons and hyperons derived within the Brueckner-Hartree-Fock many-b
ody theory with realistic two-body and three-body forces. For the description of quark matter, we use several different models, e.g. the MIT bag, the Nambu--Jona-Lasinio (NJL), the Color Dielectric (CDM), the Field Correlator method (FCM), and one based on the Dyson-Schwinger model (DSM). We find that a two solar mass hybrid star is possible only if the nucleonic EOS is stiff enough.
We study the structure of protoneutron stars within the finite-temperature Brueckner-Bethe-Goldstone theoretical approach, paying particular attention to how it is joined to a low-density nuclear equation of state (EOS). We find a slight sensitivity
of the minimum value of the protoneutron star mass on the low-density equation of state, whereas the maximum mass is hardly affected.
We study the structure of hadronic protoneutron stars within the finite temperature Brueckner-Bethe-Goldstone theoretical approach. Assuming beta-equilibrated nuclear matter with nucleons and leptons in the stellar core, with isothermal or isentropic
profile, we show that particle populations and equation of state are very similar. As far as the maximum mass is concerned, we find that its value turns out to be almost independent on T, while a slight decrease is observed in the isentropic case, due to the enhanced proton fraction in the high density range.
We explore the relevance of confinement in quark matter models for the possible quark core of neutron stars. For the quark phase, we adopt the equation of state (EoS) derived with the Field Correlator Method, extended to the zero temperature limit. F
or the hadronic phase, we use the microscopic Brueckner-Hartree-Fock many-body theory. We find that the currently adopted value of the gluon condensate $G_2 simeq 0.006-0.007 rm {GeV^4}$, which gives a critical temperature $T_c simeq 170 rm MeV$, produces maximum masses which are only marginally consistent with the observational limit, while larger masses are possible if the gluon condensate is increased.
We investigate the structure of protoneutron stars (PNS) formed by hadronic and quark matter in $beta$-equilibrium described by appropriate equations of state (EOS). For the hadronic matter, we use a finite temperature EOS based on the Brueckner-Beth
e-Goldstone many-body theory, with realistic two- and three-body forces. For the quark sector, we employ the Nambu--Jona-Lasinio model. We find that the maximum allowed masses are comprised in a narrow range around 1.8 solar masses, with a slight dependence on the temperature. Metastable hybrid protoneutron stars are not found.
The Equation of State (EoS) of dense matter represents a central issue in the study of compact astrophysical objects and heavy ion reactions at intermediate and relativistic energies. We have derived a nuclear EoS with nucleons and hyperons within th
e Brueckner-Hartree-Fock approach, and joined it with quark matter EoS. For that, we have employed the MIT bag model, as well as the Nambu--Jona-Lasinio (NJL) and the Color Dielectric (CD) models, and found that the NS maximum masses are not larger than 1.7 solar masses. A comparison with available data supports the idea that dense matter EoS should be soft at low density and quite stiff at high density.
