Hybrid stars within a covariant, nonlocal chiral quark model

Blaschke, D.; Dumm, D. Gómez; Grunfeld, A. G.; Klähn, T.; Scoccola, N. N.

doi:10.1103/physrevc.75.065804

Cited by 75 publications

(68 citation statements)

References 49 publications

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“…For stellar sequences that are based on microscopic input the stability is not a guaranteed feature. The equilibrium among the quark and nuclear phases is achieved for rather stiff nuclear equations of state, while those configurations that contain quark phase(s) often belong to unstable branches of the sequences [23,24,25,26,27,28,29]. For our microscopic input a stable branch of CCS hybrid stars emerges in the form of a "second family" of configurations, which is separated from their purely nuclear counterparts by a region of instability.…”

Section: Introductionmentioning

confidence: 99%

Gravitational radiation from crystalline color-superconducting hybrid stars

Knippel

Sedrakian

2009

Phys. Rev. D

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The interiors of high mass compact (neutron) stars may contain deconfined quark matter in a crystalline color superconducting (CCS) state. On a basis of microscopic nuclear and quark matter equations of states we explore the internal structure of such stars in general relativity. We find that their stable sequence harbors CCS quark cores with masses Mcore ≤ (0.78 − 0.82)M⊙ and radii Rcore ≤ 7 km. The CCS quark matter can support nonaxisymmetric deformations, because of its finite shear modulus, and can generate gravitational radiation at twice the rotation frequency of the star. Assuming that the CCS core is maximally strained we compute the maximal quadrupole moment it can sustain. The characteristic strain of gravitational wave emission h0 predicted by our models are compared to the upper limits obtained by the LIGO and GEO 600 detectors. The upper limits are consistent with the breaking strain of CCS matter σ ≤ 10 −4 and large pairing gaps ∆ ∼ 50 MeV, or, alternatively, with σ ∼ 10 −3 and small pairing gaps ∆ ∼ 15 MeV. An observationally determined value of the characteristic strain h0 can pin down the product σ∆ 2 . On the theoretical side a better understanding of the breaking strain of CCS matter will be needed to predict reliably the level of the deformation of CCS quark core from first principles.

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Section: Introductionmentioning

confidence: 99%

Gravitational radiation from crystalline color-superconducting hybrid stars

Knippel

Sedrakian

2009

Phys. Rev. D

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“…On the other hand, recent neutron star observations impose constraints on possible nuclear matter equations of state (EOS's). As a result, nuclear matter EOS's obtained using effective models should be consistent with astrophysical bounds in order to be used for neutron star matter calculations [4]. Recently, nuclear matter EOS's have also been investigated consistently with collective flow data from heavy ion collision experiments [5].…”

Section: Introductionmentioning

confidence: 99%

Kaon properties in (proto-)neutron star matter

et al. 2010

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The modification on kaon and antikaon properties of in the interior of (proto-)neutron stars is investigated using a chiral SU(3) model. The parameters of the model are fitted to nuclear matter saturation properties, baryon octet vacuum masses, hyperon optical potentials and low energy a kaon-nucleon scattering lengths. We study the kaon/antikaon medium modification and explore the possibility of antikaon condensation in (proto-)neutron star matter at zero as well as finite temperature/entropy and neutrino content. The effect of hyperons on kaon and antikaon optical potentials is also investigated at different stages of the neutron star evolution.

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“…The mixed phases range from 3.2 − 8.2ρ 0 , 3.8 − 8.5ρ 0 , and 4.5 − 8.9ρ 0 for vector coupling constants G V /G s = 0, 0.05, 0.1, respectively. We note that there is considerable theoretical uncertainty in the ratio of G V /G s [29] since a rigorous derivation of the effective couplings from QCD is not possible. Combining the ratios of G V /G s from the molecular instanton liquid model and from the Fierz transformation, the value of G V /G s is expected to be in the range 0 G V /G s 0.5 [30].…”

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Quark-hybrid matter in the cores of massive neutron stars

et al. 2013

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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. According to our study, the transition to pure quark matter does not occur in stable neutron stars, but is shifted to neutron stars which are unstable against radial oscillations. The implications of our study for the recently discovered, massive neutron star PSR J1614-2230, whose gravitational mass is 1.97 ± 0.04 M⊙, are that this neutron star may contain an extended region of quark-hybrid matter at it center, but no pure quark matter. Introduction -Quantum Chromodynamics (QCD) has the properties of asymptotic freedom and confinement. The former implies that in the high-momentum transfer regime, the quarks behave essentially as free particles, i.e., the interaction between two quarks due to gluon exchange is very weak. This regime can therefore be treated using perturbation theory, where the quark-gluon coupling constant serves as an expansion parameter. For this momentum range, the dispersion processes can be calculated very accurately. By contrast, at low-momentum transfers ( 1 GeV) QCD becomes highly nonlinear, which prevents the use of perturbative methods. One of the renowned effective models that serves as a suitable approximation to QCD in the low-energy regime is the quark version of the Nambu JonaLasinio (NJL) model [1][2][3]. In this model chiral symmetry constraints are taken into account via effective interactions between quarks, through local four-point vertex interactions. The drawbacks of using local interactions are that the model must be regularized to avoid divergences in the loop integrals, and that the model is non-confining. The absence of confinement is essentially related to the fact that the dynamically generated constituent quark masses are momentum independent. Since the 1990's, there have been investigations proposing nonlocal interactions to solve these problems [4]. One interesting suggestion arises from the relationship between the NJL model and the model of one-gluon exchange where an effective gluon propagator is used to generate effective interactions between quarks. This provides a natural way to introduce a nonlocality in the quark-quark interaction, which can be characterized by a model-dependent form factor, g(p) [5].In this paper we analyze the global structure and composition of massive neutron stars in the framework of an extended version of the nonlocal SU(3) NJL model. Of particular interest is the question as to whether or not massive neutron stars, such as the recently discovered pulsar PSR J1614-2230 whose gravitational mass was found to be 1.97 ± 0.04 M ⊙ [6], may contain stellar cores made of deconfined quark matter [7][8][9]16]. Tendentially, one could argue that quark deconfinement may not...

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Hybrid stars within a covariant, nonlocal chiral quark model

Cited by 75 publications

References 49 publications

Gravitational radiation from crystalline color-superconducting hybrid stars

Gravitational radiation from crystalline color-superconducting hybrid stars

Kaon properties in (proto-)neutron star matter

Quark-hybrid matter in the cores of massive neutron stars

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