Lennard-Jones quark matter and massive quark stars

Lai, Xiaoyu; Xu, R. X.

doi:10.1111/j.1745-3933.2009.00701.x

Cited by 87 publications

(102 citation statements)

References 28 publications

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“…For the sake of simplicity, the interaction between two strangeons is assumed to be LennardJones-like [6], which is similar to the interaction between atom of inert gas,…”

Section: A Corresponding State Approach and Resultsmentioning

confidence: 99%

Strangeon Matter in a Liquid Drop Model

Wang

2018

Proceedings of the Workshop on Quarks and Compact Stars 2017 (QCS2017)

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The liquid drop model of 2-flavored (u and d) nucleus is well known and successful, analogically, a similar drop model for 3-flavored (u, d and s) nucleus is developed. A 3-flavored nucleus conjectured could be stable only if its baryon number is larger than a critical one, A c , in which strangeons are the constituent as an analogy of nucleons for nucleus [1]. We try to model strangeon matter in a sense of phenomenological liquid drop, with two free parameters: the mass per baryon of a strangeon in vacuum, M, and potential depth between strangeons, ϵ. It is found that, for M ∼ GeV and ϵ ∼ 100 MeV, strangeon matter could be stable and its critical number could be as low as A c = 300. KEYWORDS: pulsar: general, dense matter, equation of stateThe Witten's conjecture [2] about dense matter could be extended to a generalized version: strange matter in bulk could be absolutely stable, in which quarks are either free (for strange quark matter) or localized (for strangeon matter) [1,3]. A strangeon may contain equal numbers of u, d and s quarks, and its number of quarks inside could be 6, 9, 12, 18 or even more. The interaction between strangeons could be similar to that between nucleons (i.e., Lennard-Jones-like), and consequently, it might then be rational to have a description of strangeon matter based on this liquid drop scenario, a model that has already been certified for nucleus and is always introduced in standard text books.Strangeon matter, formerly known as solid quark matter [3], is conjectured when chiral symmetry is broken in the QCD phase-diagram. However, a quarkyonic phase is suggested when chiral symmetry is restored but quarks are confined [4]. The color interaction between quarks in the strangeon phase might be stronger than that inside quarkyonic matter, but the details yet remains unclear. A Model of Strangeon MatterIn the conventional liquid drop model of nucleus, there are terms of volume, surface, Coulomb, and others [5],where A and Z are the baryon number and proton number of the nucleus; I = (N − Z)/A, represents the asymmetry of the nucleus; M p and M n are the mass of proton and neutron; b vol , k vol , b surf , k surf and r 0 are the parameters of the model. In analogy to the drop model of nucleus, a liquid drop model could be constructed for strangeon matter. The asymmetry energy, however, could be negligible due to three-flavor symmetry restoration, whereas the volume and surface terms remain, and the energy per baryon of a strangeon drop could

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“…For the sake of simplicity, the interaction between two strangeons is assumed to be LennardJones-like [6], which is similar to the interaction between atom of inert gas,…”

Section: A Corresponding State Approach and Resultsmentioning

confidence: 99%

Strangeon Matter in a Liquid Drop Model

Wang

2018

Proceedings of the Workshop on Quarks and Compact Stars 2017 (QCS2017)

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“…Strangeon ["streIdZI6n] is a new word, formerly known as strange quark-cluster [2][3][4], and is actually coined by combining "strange nucleon". This word is created to describe a new kind of constituent similar to nucleon but with strangeness, being also regarded as an abbreviation of strange nucleon.…”

Section: What Is a Strangeon?mentioning

confidence: 99%

Strangeon Stars

Lu¹,

Xu²

2018

Proceedings of the Workshop on Quarks and Compact Stars 2017 (QCS2017)

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Stable micro-nucleus is 2-flavored (u and d), whereas stable macro-nucleus could be 3-flavored (u, d and s) if the light flavor symmetry restores there. Nucleons are the constituent of a nucleus, while strangeons are named as the constituent of 3-flavored baryonic matter. Gravity-compressed baryonic object created after core-collapse supernova could be strangeon star if the energy scale (∼ 0.5 GeV) cannot be high enough for quark deconfinement and if there occurs 3-flavor symmetry restoration. Strangeon stars are explained here, including their formation and manifestation/identification. Much work, coupled with effective micro-model of strangeon matter, is needed to take advantage of the unique opportunities advanced facilities will provide. KEYWORDS: pulsar: general, dense matter, equation of stateAlthough the state equation of dense matter around nuclear density is a great challenge for physicists, it is usually a thought that strangeness could be relevant to the solution. As noted in the QC-S2014 proceedings [1], such kind of strange matter is conjectured to be strangeon matter, being manifested in the form of compact stars, cosmic rays, and even dark matter. In this contribution, we are focusing on strangeon star, which is a key ingredient of strangeon matter in astrophysics.It is half a century since the first pulsar was discovered, but the real nature of pulsar remains one of the most puzzling problems both in physics and in astronomy. Pulsars are always thought to be neutron stars, but the issue of their real structure is still controversial. Different observations (e.g., the spin period, the measurements of mass and radius) show that the typical density of pulsar-like compact stars could be only a few nuclear density, and the separation between quarks is ∼ 0.5 fm and hence the energy scale is order of ∼ 0.5 GeV according to Heisenberg's uncertainty relation. The pulsar structure is then a problem of non-perturbative QCD (quantum chromo-dynamics), an unsolved issue for fundamental strong interaction at low energy regime ( 1 GeV). Similar to the issue of turbulence, the strong interaction physics at low-energy is still challenging though QCD is mathematically well-defined. In fact, both of "Navier-Stokes Equation" and "Yang-Mills and Mass Gap" are prize problems named by the Clay Mathematical Institute. Hitherto now, no one can derive pulsar structure from ab-initio calculations, nonetheless astrophysicists could speculate phenomenologically.In Fig. 1, we summarize pulsar inner structures (i.e., models) speculators suggest. All of the pulsar structure models fell into four categories: hadron star, quark star, hybrid/mixed star and strangeon star, as are shown in Fig. 1. In the hadron star model, quarks are confined in hadrons, and the hadron liquid is the dominated part of the star. Hadron stars are bounded by gravity, and they must have crusts composed of ions and electrons. A hadron star is called a neutron star if only the nucleon (proton and neutron) degree of freedom is introduced. Conversely, a quark...

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“…The SQS could has a larger maximum mass than other model of quark stars. Lai & Xu (2009) gives a maximum mass > 2M⊙, which stands the test of the 2 M⊙ pulsar (Demorest et al 2010). The SQS has a smaller radius than any NSs when the mass is small.…”

Section: Introductionmentioning

confidence: 99%

“…The newly confirmed mass of PSR J1614-2230 of 2M⊙ (Demorest et al 2010) rules out almost all currently proposed hyperon or boson condensate EoSs (Lattimer & Prakash 2007) and traditional soft EoS of SS (Chan et al 2009). Lai & Xu (2009) argued that the solid quark-cluster stars (SQS), a special kind of SS, could have the maximum mass to be larger than 2 M⊙ because of the very stiff EoS.…”

Section: Introductionmentioning

confidence: 99%

“…the SQS , is still survived theoretically. The SQS is suggested by Xu (2003) and improved by Zhou et al (2004), Lai & Xu (2009) and . The key point is that the interaction energy of quarks in a compact star could be higher than the Fermi energy when the density is lower than a few tens of nuclear densities (Xu 2011), so that quarks may be clustered and the star could be a solid star, i.e.…”

Section: Introductionmentioning

confidence: 99%

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The missing compact star of SN1987A: a solid quark star?

Liu¹,

Liang

Xu³

et al. 2012

Proc. IAU

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To investigate the missing compact star of Supernova 1987A, we analyzed both the cooling and the heating processes of a possible compact star based on the upper limit of observational X-ray luminosity. From the cooling process we found that a solid quark-cluster star, which has a stiffer equation of state than that of conventional liquid quark star, has a heat capacity much smaller than a neutron star. It can cool down quickly, which can naturally explain the nondetection of a point source (neutron star or quark star) in X-ray band. On the other hand, we consider the heating process from magnetospheric activity and possible accretion, and obtain some constraints to the parameters of a possible pulsar. We conclude that a solid quark-cluster star can be fine with the observational limit in a large and acceptable parameter space. A pulsar with a short period and a strong magnetic field (or with a long period and a weak field) would has luminosity higher than the luminosity limit if the optical depth is not large enough to hide the compact star. The constraints of the pulsar parameters can be tested if the central compact object in 1987A is discovered by advanced facilities in the future.

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Lennard-Jones quark matter and massive quark stars

Cited by 87 publications

References 28 publications

Strangeon Matter in a Liquid Drop Model

Strangeon Matter in a Liquid Drop Model

Strangeon Stars

The missing compact star of SN1987A: a solid quark star?

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