Quark stars within relativistic models

Menezes, D. P.; Providência, Constança; Melrose, D. B.

doi:10.1088/0954-3899/32/8/001

Cited by 81 publications

(68 citation statements)

References 64 publications

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“…Moreover, in Ref. [55] it was shown that within the NJL a much larger electron chemical potential is expected at the surface, allowing more easily for a mantle to exist. Understanding how this mantle could be affected in the presence of a magnetic field is an interesting question that, however, is beyond the scope of the present work.…”

Section: Resultsmentioning

confidence: 99%

“…This effect is clearly seen by comparing the pressure for ρ = 3ρ 0 corresponding to u and d quark matter with restored chiral symmetry with the pressure obtained for either ρ = 2ρ 0 or ρ = 5ρ 0 as a function of B: In the first case chiral symmetry is still not completely restored and in the second the onset of s quark has occurred. If a quark model with complete chiral symmetry restored, such 065205-8 as the MIT bag model, or a model without the strangeness degree of freedom, such as the su(2) NJL, is used to describe β-equilibrium quark matter, a different behavior will probably occur for B 10 18 G and ρ > 0.5 fm −3 right until the star center, e.g., ρ ∼ 1.2 fm −3 [21,55]; in particular, both pressure contributions will be coincident.…”

Section: Final Remarksmentioning

confidence: 99%

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Anisotropy in the equation of state of magnetized quark matter

2015

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The anisotropies in the pressure obtained from the energy-momentum tensor are studied for magnetized quark matter within the su(3) Nambu-Jona-Lasinio model for both β-equilibrium matter and quark matter with equal quark chemical potentials. The effect of the magnetic field on the particle polarization, magnetization, and quark matter constituents is discussed. It is shown that the onset of the s quark after chiral symmetry restoration of the u and d quarks gives rise to a special effect on the magnetization in the corresponding density range: A quite small magnetization just before the s onset is followed by a strong increase of this quantity as soon as the s quark sets in. It is also demonstrated that for B < 10 18 G within the two scenarios discussed, always considering a constant magnetic field, the two components of pressure are practically coincident. The structure of the QCD phase diagram is of utmost importance in understanding many physical aspects of nature, ranging from the early universe to possible nuclear liquid-gas and hadronic quark matter phase transitions to the physics of compact objects [1]. Early analyzes performed within the Nambu-Jona-Lasinio model (NJL) framework indicate that when strongly interacting matter is subject to intense magnetic fields the QCD phase diagram boundaries are modified [2]. Some of the most important changes concern the size and location of the first-order chiral transition region since the results show that a strong magnetic field favors this type of transition. At the same time, at low temperatures, the value of the coexistence chemical potential decreases as B increases in accordance with the inverse magnetic catalysis (ICM) phenomenon [3].The low-T and high-μ region where a first-order-type transition is expected to occur is currently unavailable to lattice QCD evaluations (LQCD). However, the region high-T and low-μ has already been exploited using LQCD simulations which indicate, in accordance with most model predictions, that the crossover observed at B = 0 persists when B = 0 [4][5][6][7]. On the other hand, a major disagreement between recent LQCD results [6,7] and model calculations regards the dependence of crossover pseudocritical temperature, T pc , on the strength B of the magnetic field. Specifically, the lattice results of Refs. [6,7], performed with 2 + 1 quark flavors and physical pion mass values, predict an inverse catalysis, with T pc decreasing with B, while effective models predict an increase of T pc with B. This problem has been recently addressed by different groups [8,9], who basically agree that the different results stem from the fact that most effective models miss back reaction effects (the indirect interaction of gluons and B) as well as the QCD asymptotic freedom phenomenon. At the same time, other important aspects of the effects of strong magnetic fields on the QCD phase diagram have already been studied, including the behavior of the coexistence chemical potential and the location of the critical end point (CEP) [10], the dependenc...

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Section: Resultsmentioning

confidence: 99%

Section: Final Remarksmentioning

confidence: 99%

Anisotropy in the equation of state of magnetized quark matter

2015

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“…5, a mass-radius plot of compact object. Theoretically, pulsars may consist of hadronic matter only (Menezes & Providência 2004a), hadronic and quark matter (hybrid stars) either bearing or not a mixed phase (Menezes & Providência 2004b;Panda et al 2004;Tatsumi et al 2003) or quark matter only (Menezes et al 2006a;Ivanov et al 2005;Li et al 1999). All calculations depend on choosing of appropriate equations of state based on nuclear physics and thermodynamics requirements, which enter as input to the Tolman-OppenheimerVolkoff equations.…”

Section: Pulsar: Neutron Star or Quark Star?mentioning

confidence: 99%

Study of measured pulsar masses and their possible conclusions

Zhang

Wang

Zhao

et al. 2011

A&A

147

116

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We study the statistics of 61 measured masses of neutron stars (NSs) in binary pulsar systems, including 18 double NS (DNS) systems, 26 radio pulsars (10 in our Galaxy) with white dwarf (WD) companions, 3 NSs with main-sequence companions, 13 NSs in X-ray binaries, and one undetermined system. We derive a mean value of M = 1.46 ± 0.30 M . When the 46 NSs with measured spin periods are divided into two groups at 20 milliseconds, i.e., the millisecond pulsar (MSP) group and others, we find that their mass averages are, respectively, M = 1.57 ± 0.35 M and M = 1.37 ± 0.23 M . In the framework of the pulsar recycling hypothesis, this suggests that an accretion of approximately ∼0.2 M is sufficient to spin up a neutron star and place it in the millisecond pulsar group. Based on these estimates, an approximate empirical relation between the accreting mass (ΔM) of recycled pulsar and its spin period is proposed as ΔM = 0.43 (M )(P/1 ms) −2/3 . If we focus only on the DNS, the mass average of all 18 DNSs is 1.32 ± 0.14 M , and the mass averages of the recycled DNSs and the non-recycled NS companions are, respectively, 1.38 ± 0.12 M and 1.25 ± 0.13 M . This is consistent with the hypothesis that the masses of both NSs in DNS system have been affected by accretion. The mass average of MSPs is higher than the Chandrasekhar limit 1.44 M , which may imply that most of binary MSPs form via the standard scenario by accretion recycling. If we were to assume that the mass of a MSP formed by the accretion induced collapse (AIC) of a white dwarf must be less than 1.35 M , then the portion of the binary MSPs involved in the AICs would not be higher than 20%, which imposes a constraint on the AIC origin of MSPs. With accreting mass from the companion, the nuclear matter composition of MSP may experience a transition from the "soft" equation of state (EOS) to a "stiff" EOS or even neutron to quark matter.

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“…Typically this abundance does not exceed 1/3 [19]. We mentioned above that we can take that n u = n d = n s = n 0 /3 in QS as a limiting case.…”

Section: Introductionmentioning

confidence: 99%

Magnetic fields in turbulent quark matter and magnetar bursts

Dvornikov

2017

Int. J. Mod. Phys. D

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We analyze the magnetic field evolution in dense quark matter with unbroken chiral symmetry, which can be found inside quark and hybrid stars. The magnetic field evolves owing to the chiral magnetic effect in the presence of the electroweak interaction between quarks. In our study, we also take into account the magnetohydrodynamic turbulence effects in dense quark matter. We derive the kinetic equations for the spectra of the magnetic helicity density and the magnetic energy density as well as for the chiral imbalances. On the basis of the numerical solution of these equations, we find that turbulence effects are important for the behavior of small scale magnetic fields. It is revealed that, under certain initial conditions, these magnetic fields behave similarly to the electromagnetic flashes of some magnetars. We suggest that fluctuations of magnetic fields, described in frames of our model, which are created in the central regions of a magnetized compact star, can initiate magnetar bursts.

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Quark stars within relativistic models

Cited by 81 publications

References 64 publications

Anisotropy in the equation of state of magnetized quark matter

Anisotropy in the equation of state of magnetized quark matter

Study of measured pulsar masses and their possible conclusions

Magnetic fields in turbulent quark matter and magnetar bursts

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