On the Transport Properties of a Quark-Hadron Coulomb Lattice in the Cores of Neutron Stars (original) (raw)

Massive quarks in neutron stars

Physics Letters B, 1996

We study various neutron star properties using the Color-Dielectric model to describe quark matter. For the baryon sector at low densities we employ the Walecka model. Applying Gibbs criteria to this composite system, we find that, for matter at r-equilibrium, the pure hadronic phase ends at 0.11 fm -3 and that the mixed quark and hadronic phase extends to 0.31 fm -3. The resulting equation of state yields a maximum nefitron star mass of 1.59M®. A neutron star with total mass of 1.4M® will consist of a crust made of hadronic matter only, a ~ 1 km thick region of mixed phase and a core composed of pure quark matter. Implications for the cooling of neutron stars are discussed.

Phases of Hadron-Quark Matter in (Proto) Neutron Stars

Universe

In the first part of this paper, we investigate the possible existence of a structured hadron-quark mixed phase in the cores of neutron stars. This phase, referred to as the hadron-quark pasta phase, consists of spherical blob, rod, and slab rare phase geometries. Particular emphasis is given to modeling the size of this phase in rotating neutron stars. We use the relativistic mean-field theory to model hadronic matter and the non-local three-flavor Nambu–Jona-Lasinio model to describe quark matter. Based on these models, the hadron-quark pasta phase exists only in very massive neutron stars, whose rotational frequencies are less than around 300 Hz. All other stars are not dense enough to trigger quark deconfinement in their cores. Part two of the paper deals with the quark-hadron composition of hot (proto) neutron star matter. To this end we use a local three-flavor Polyakov–Nambu–Jona-Lasinio model which includes the ’t Hooft (quark flavor mixing) term. It is found that this term ...

Quark-hybrid matter in the cores of massive neutron stars

2013

Using a nonlocal extension of the SU(3) Nambu-Jona Lasinio model, which reproduces several of the key features of Quantum Chromodynamics, we show that mixed phases of deconfined quarks and confined hadrons (quark-hybrid matter) may exist in the cores of neutron stars as massive as around 2.1 M ⊙ . The radii of these objects are found to be in the canonical range of ∼ 12 − 13 km.

Anomalous thermodynamics and phase transitions in neutron star matter

Physical Review C, 2007

The presence of the long-range Coulomb force in dense stellar matter implies that the total charge cannot be associated with a chemical potential, even if it is a conserved quantity. As a consequence, the analytical properties of the partition sum are modified, changing the order of the phase transitions and affecting the possible occurrence of critical behaviours. The peculiar thermodynamic properties of this system can be understood introducing a model hamiltonian where each charge is independently neutralized by a uniform background of opposite charge. Some consequences on the characteristics of mixed-phase structures in neutron star crusts and supernova cores are discussed.

Neutron star interiors and the equation of state of ultra-dense matter

2006

Neutron stars contain matter in one of the densest forms found in the Universe. This feature, together with the unprecedented progress in observational astrophysics, makes such stars superb astrophysical laboratories for a broad range of exciting physical studies. This paper gives an overview of the phases of dense matter predicted to make their appearance in the cores of neutron stars. Particular emphasis is put on the role of strangeness. Net strangeness is carried by hyperons, K-mesons, H-dibaryons, and strange quark matter, and may leave its mark in the masses, radii, moment of inertia, dragging of local inertial frames, cooling behavior, surface composition, and the spin evolution of neutron stars. These observables play a key role for the exploration of the phase diagram of dense nuclear matter at high baryon number density but low temperature, which is not accessible to relativistic heavy ion collision experiments.

Quark Matter in Neutron Stars: An Aperçu

Modern Physics Letters A, 2006

The existence of deconfined quark matter in the superdense interior of neutron stars is a key question that has drawn considerable attention over the past few decades. Quark matter can comprise an arbitrary fraction of the star, from 0 for a pure neutron star to 1 for a pure quark star, depending on the equation of state of matter at high density. From an astrophysical viewpoint, these two extreme cases are generally expected to manifest different observational signatures. An intermediate fraction implies a hybrid star, where the interior consists of mixed or homogeneous phases of quark and nuclear matter, depending on surface and Coulomb energy costs, as well as other finite size and screening effects. In this brief review article, we discuss what we can deduce about quark matter in neutron stars in light of recent exciting developments in neutron star observations. We state the theoretical ideas underlying the equation of state of dense quark matter, including color superconducting quark matter. We also highlight recent advances stemming from re-examination of an old paradigm for the surface structure of quark stars and discuss possible evolutionary scenarios from neutron stars to quark stars, with emphasis on astrophysical observations.

Camouflage of the Phase Transition to Quark Matter in Neutron Stars

The Astrophysical Journal

It has been known for some time that compact stars containing quark matter can masquerade as neutron stars in the range of measured mass and radius, making it difficult to draw firm conclusions on the phases of matter present inside the star. Using the vector-enhanced Bag model (vBag), we examine mass-radius and mass-compactness relations with Maxwell and Gibbs construction for hybrid stars with transitions from nuclear matter to two or three-flavor quark matter, including sequential transitions. Not only can stable hybrid stars with either two or three flavor quark matter mimic neutron stars (the traditional masquerade), it appears as well difficult to distinguish twoflavor from three-flavor quark matter even in cases where a phase transition can be said to have occurred, as in the presence of a distinct kink in the mass-radius relation. Furthermore, allowing for sequential flavor transitions, we find that the transition into an unstable branch can be caused by either a transition from a nuclear to unstable quark matter or the sequential transition from nuclear to stable but "masquerading" two-flavor to unstable three-flavor quark matter. Addressing chiral restoration as well as quark deconfinement in a model of the phase transition, as the vBag does, adds further flexibility to the high-density equation of state, motivating caution in using even high-precision M-R data to draw firm conclusions on the nature of phases and phase transitions in neutron stars.

Formation Of Quark Matter In Neutron Stars

At very large densities and/or temperatures a quark-hadron phase transition is expected to take place. Simulations of QCD on lattice at zero baryon density indicate that the transition occurs at Tc ∼ 150 − 170 MeV. The calculations indicate that transition is likely to be second order or a cross over phenomenon. Although the lattice simulations have not given any indication on when the transition occurs at nonzero baryon density, the transition is expected to occur around the densities of few times nuclear matter density. Also, there is a strong reason to believe that the quark matter formed after the phase transition is in colour superconducting phase. The matter densities in the interior of neutron stars are expected to be several times the nuclear matter density and therefore the neutron star cores may possibly consist of quark matter. One then expects that this quark matter is formed during the collapse of supernova. Starting with the assumption that the quark matter, when formed consists of predominantly u and d quarks, we consider the evolution of strange quarks by weak interactions in the present work. The reaction rates and time required to reach the chemical equilibrium are computed here. Our calculations show that the chemical equilibrium is reached in about 10 −7 seconds. Further more during and immediately after the equilibration process enormous amount of energy is released and copious numbers of neutrinos are produced. We show that for reasonable models of nuclear equations of state the amount of energy released could be as high as 10 53 ergs and as many as 10 58 neutrinos may be emitted during the quark matter formation.

From hadrons to quarks in neutron stars: a review

Reports on progress in physics. Physical Society (Great Britain), 2018

In recent years our understanding of neutron stars has advanced remarkably, thanks to research converging from many directions. The importance of understanding neutron star behavior and structure has been underlined by the recent direct detection of gravitational radiation from merging neutron stars. The clean identification of several heavy neutron stars, of order two solar masses, challenges our current understanding of how dense matter can be sufficiently stiff to support such a mass against gravitational collapse. Programs underway to determine simultaneously the mass and radius of neutron stars will continue to constrain and inform theories of neutron star interiors. At the same time, an emerging understanding in quantum chromodynamics (QCD) of how nuclear matter can evolve into deconfined quark matter at high baryon densities is leading to advances in understanding the equation of state of the matter under the extreme conditions in neutron star interiors. We review here the eq...

Neutron stars and the equation of state

Journal of Astrophysics and Astronomy, 2018

The interior of neutron stars consists of the densest, although relatively cold, matter known in the universe. Here, baryon number densities might reach values close to ten times the nuclear saturation density. These suggest that the constituents of neutron star cores not only consist of nucleons, but also of more exotic baryons like hyperons or a phase of deconfined quarks. We discuss the consequences of such exotic particles on the gross properties and phenomenology of neutron stars. In addition, we determine the general phase structure of dense and also hot matter in the chiral parity-doublet model and confront model results with the recent constraints derived from the neutron star merger observation.