Impact of the neutron-star deformability on equation of state parameters

Tsang, C. Y.; Tsang, M. B.; Danielewicz, Pawel; Lynch, W. G.; Fattoyev, F. J.

doi:10.48550/arxiv.2009.05239

Cited by 2 publications

(4 citation statements)

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“…The point with errorbars labeled "Tsang et al" represents the results reported in Ref. [8] based on a Taylor expansion of the symmetry energy around the saturation density and neutron-star properties. The line labelled "approx."…”

Section: A Constraints On and Correlations Between Symmetry-energy Pa...mentioning

confidence: 99%

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Constraining the density dependence of the symmetry energy with nuclear data and astronomical observations in the Korea-IBS-Daegu-SKKU framework

et al. 2021

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Background: The properties of very neutron rich nuclear systems are largely determined by the density dependence of the nuclear symmetry energy. The KIDS framework for the nuclear equation of state (EoS) and energy density functional (EDF) offers the possibility to explore the symmetryenergy parameters such as J (value at saturation density), L (slope at saturation), Ksym (curvature at saturation) and higher-order ones independently of each other and independently of assumptions about the in-medium effective mass, as previously shown in the cases of closed-shell nuclei and neutron-star properties. Purpose: We examine the performance of EoSs with different symmetry energy parameters on properties of nuclei and observations of neutron stars and gravitational waves in an effort to constrain in particular L and Ksym or the droplet-model counterpart Kτ . Method: Assuming a standard EoS for symmetric nuclear matter, we explore several points on the hyperplane of (J, L, Ksym or Kτ ) values. For each point, the corresponding KIDS functional parameters and a pairing parameter are obtained for applications in spherical even-even nuclei. This is the first application of KIDS energy density functionals with pairing correlations in a spherical HFB computational code. The different EoSs are tested successively on the properties of closed-shell nuclei, along the Sn isotopic chain, and on astronomical observations, in a step-by-step procedure of elimination and correction. Results: A small regime of best-performing parameters is determined and correlations between symmetry-energy parameters are critically discussed. The results strongly suggest that Ksym is negative and no lower than −200 MeV, that Kτ lies between roughly −400 and −300 MeV and that L lies between 40 and 65 MeV, with L 55MeV more likely. For the selected well-performing sets, corresponding predictions for the position of the neutron drip line and the neutron skin thickness of selected nuclei are reported. The results are only weakly affected by the choice of effective mass values. Parts of the drip line can be sensitive to the symmetry energy parameters. Conclusion: Using KIDS EoSs for unpolarized homogeneous matter at zero temperature and KIDS EDFs with pairing correlations in spherical symmetry we have explored the hyperplane of symmetryenergy parameters. Using both nuclear-structure data and astronomical observations as a testing ground, a narrow regime of well-performing parameters has been determined, free of non-physical correlations and decoupled from constraints on the nucleon effective mass. The results underscore the role of Kτ and of precise astronomical observations. More-precise constraints are possible with precise fits to nuclear energies and, in the future, more-precise input from astronomical observations.

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Section: A Constraints On and Correlations Between Symmetry-energy Pa...mentioning

confidence: 99%

“…On the other hand, it is not easy to apply to nuclei beyond the Thomas-Fermi approximation [7] and in addition there are diverse strategies for correcting the EoS near zero density -see also Ref. [8] about this issue.…”

Section: Introductionmentioning

confidence: 99%

Constraining the density dependence of the symmetry energy with nuclear data and astronomical observations in the Korea-IBS-Daegu-SKKU framework

et al. 2021

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“…These HM EOSs are often restricted by the underlying energy density functionals of the theories used and are usually not flexible enough in statistical analyses to explore the whole EOS parameter space permitted by general physics principles and known constraints as pointed out already in Refs. [22,31]. On equal footing as the generic QM EOS, we use the meta-model of Ref.…”

Section: Theoretical Approachmentioning

confidence: 99%

“…[32,33] and astrophysics applications, see, e.g., Refs. [2,22,25,31,[34][35][36][37][38][39][40][41]. For this work, we calculate the pressure within the npeµ model for the core of NSs using…”

Section: Theoretical Approachmentioning

confidence: 99%

Bayesian inference of dense matter EOS encapsulating a first-order hadron-quark phase transition from observables of canonical neutron stars

Xie,

2020

Preprint

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Background: The remarkable progress in recent multimessenger observations of both isolated neutron stars (NSs) and their mergers has provided some of the much needed data to improve our understanding about the Equation of State (EOS) of dense neutron-rich matter. Various EOSs with or without some kinds of phase transitions from hadronic to quark matter (QM) have been widely used in many forward-modelings of NS properties. Direct comparisons of these predictions with observational data sometimes also using χ 2 minimizations have provided very useful constraints on the model EOSs. However, it is normally difficult to perform uncertain quantifications and analyze correlations of the EOS model parameters involved in forward-modelings especially when the available data are still very limited.Purpose: We infer the posterior probability distribution functions (PDFs) and correlations of nine parameters characterizing the EOS of dense neutron-rich matter encapsulating a first-order hadron-quark phase transition from the radius data of canonical NSs reported by LIGO/VIRGO, NICER and Chandra Collaborations. We also infer the QM mass fraction and its radius in a 1.4 M⊙ NS and predict their values in more massive NSs.Method: Meta-modelings are used to generate both hadronic and QM EOSs in the Markov-Chain Monte Carlo sampling process within the Bayesian statistical framework. An explicitly isospin-dependent parametric EOS for the npeµ matter in NSs at β equilibrium is connected through the Maxwell construction to the QM EOS described by the constant speed of sound (CSS) model of Alford, Han and Prakash.Results:(1) The most probable values of the hadron-quark transition density ρt/ρ0 and the relative energy density jump there ∆ε/εt are ρt/ρ0 = 1.6 +1.2 −0.4 and ∆ε/εt = 0.4 +0.20 −0.15 at 68% confidence level, respectively. The corresponding probability distribution of QM fraction in a 1.4 M⊙ NS peaks around 0.9 in a 10 km sphere. Strongly correlated to the PDFs of ρt and ∆ε/εt, the PDF of the QM speed of sound squared c 2 QM /c 2 peaks at 0.95 +0.05 −0.35 , and the total probability of being less than 1/3 is very small. (2) The correlations between PDFs of hadronic and QM EOS parameters are very weak. While the most probable values of parameters describing the EOS of symmetric nuclear matter remain almost unchanged, the high-density symmetry energy parameters of neutron-rich matter are significant different with or without considering the hadron-quark phase transition. Conclusions:The available astrophysical data considered together with all known EOS constraints from theories and terrestrial nuclear experiments prefer the formation of a large volume of QM even in canonical NSs.

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Impact of the neutron-star deformability on equation of state parameters

Cited by 2 publications

References 53 publications

Constraining the density dependence of the symmetry energy with nuclear data and astronomical observations in the Korea-IBS-Daegu-SKKU framework

Constraining the density dependence of the symmetry energy with nuclear data and astronomical observations in the Korea-IBS-Daegu-SKKU framework

Bayesian inference of dense matter EOS encapsulating a first-order hadron-quark phase transition from observables of canonical neutron stars

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