6 research outputs found
How strange are compact star interiors ?
We discuss a Nambu--Jona-Lasinio (NJL) type quantum field theoretical
approach to the quark matter equation of state with color superconductivity and
construct hybrid star models on this basis. It has recently been demonstrated
that with increasing baryon density, the different quark flavors may occur
sequentially, starting with down-quarks only, before the second light quark
flavor and at highest densities also the strange quark flavor appears. We find
that color superconducting phases are favorable over non-superconducting ones
which entails consequences for thermodynamic and transport properties of hybrid
star matter. In particular, for NJL-type models no strange quark matter phases
can occur in compact star interiors due to mechanical instability against
gravitational collapse, unless a sufficiently strong flavor mixing as provided
by the Kobayashi-Maskawa-'t Hooft determinant interaction is present in the
model. We discuss observational data on mass-radius relationships of compact
stars which can put constraints on the properties of dense matter equation of
state.Comment: 7 pages, 2 figures, to appear in the Proceedings of the International
Conference SQM2009, Buzios, Rio de Janeiro, Brazil, Sep.27-Oct.2, 200
Core collapse supernovae in the QCD phase diagram
We compare two classes of hybrid equations of state with a hadron-to-quark
matter phase transition in their application to core collapse supernova
simulations. The first one uses the quark bag model and describes the
transition to three-flavor quark matter at low critical densities. The second
one employs a Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model with
parameters describing a phase transition to two-flavor quark matter at higher
critical densities. These models possess a distinctly different temperature
dependence of their transition densities which turns out to be crucial for the
possible appearance of quark matter in supernova cores. During the early post
bounce accretion phase quark matter is found only if the phase transition takes
place at sufficiently low densities as in the study based on the bag model. The
increase critical density with increasing temperature, as obtained for our PNJL
parametrization, prevents the formation of quark matter. The further evolution
of the core collapse supernova as obtained applying the quark bag model leads
to a structural reconfiguration of the central proto-neutron star where, in
addition to a massive pure quark matter core, a strong hydrodynamic shock wave
forms and a second neutrino burst is released during the shock propagation
across the neutrinospheres. We discuss the severe constraints in the freedom of
choice of quark matter models and their parametrization due to the recently
observed 2 solar mass pulsar and their implications for further studies of core
collapse supernovae in the QCD phase diagram.Comment: 19 pages, 4 figures, CPOD2010 conference proceedin
Implications of the measurement of pulsars with two solar masses for quark matter in compact stars and heavy-ion collisions: A Nambu-Jona-Lasinio model case study
Klaehn T, Lastowiecki R, Blaschke D. Implications of the measurement of pulsars with two solar masses for quark matter in compact stars and heavy-ion collisions: A Nambu-Jona-Lasinio model case study. Physical Review D. 2013;88(8): 085001.The precise measurements of the high masses of the pulsars PSR J1614 - 2230 (M-1614 = 1.97 +/- 0.04M(circle dot)) and PSR J0348 - 0432 (M-0348 = 2.01 +/- 0.04M(circle dot)) provide an important constraint for the equation of state of cold, dense matter and are suited to give interesting insights regarding the nature and existence of the possible phase transition to deconfined quark matter in the cores of neutron stars. We analyze the stability and composition of compact star sequences for a class of hybrid nuclear-quark-matter equations of state. The quark matter phase is described in the framework of a standard color superconducting 3-flavor Nambu-Jona-Lasinio model, and the hadronic phase is given by the Dirac-Brueckner-Hartree-Fock equation of state for the Bonn-A potential. The phase transition is obtained by a Maxwell construction. Within this model setup, we aim to constrain otherwise not strictly fixed parameters of the Nambu-Jona-Lasinio model, namely, the coupling strengths in the vector meson and diquark interaction channels. We perform this investigation for two different parametrizations characterized by a different scalar coupling constant. The analysis of flow data obtained in heavy-ion collisions resulted in a further constraint that we account for in our discussion. Massive hybrid stars with extended quark matter cores can be obtained in accordance with all of the considered constraints
Neutron star matter in a modified PNJL model
We discuss a three-flavor Nambu-Jona-Lasinio model for the quark matter equation of state with scalar diquark interaction, isoscalar vector interaction and Kobayashi-Maskawa-t Hooft interaction. We adopt a phenomenological scheme to include possible effects of a change in the gluon pressure at finite baryon density by including a parametric dependence of the Polyakov-loop potential on the chemical potential. We discuss the results for the mass-radius relationships for hybrid neutron stars constructed on the basis of our model EoS in the context of the constraint from the recently measured mass of (1.97 +- 0.04) M (J ) for the pulsar PSR J1614-2230