Possible ambiguities in the equation of state for neutron stars

Cheoun, Myung-Ki; Miyatsu, Tsuyoshi; Ryu, C. Y.; Deliduman, Cemsinan; Güngör, Can; Keleş, Vildan; Kajino, Toshitaka; Mathews, Grant J.

doi:10.1063/1.4874103

Cited by 10 publications

(19 citation statements)

References 13 publications

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“…However, special relations between α and β exists and such cases correspond to some special theories: for example, β = −3α correspond to the Weyl tensor squared modification of general relativity [28,29], and β = −4α has unique energy properties [30]. The effect of the value of α, while β = 0, on the mass-radius (M-R) relation of neutron stars has been studied, for a polytropic EoS in [31], and for realistic EoS in [32,33]. These latter works constrained the value of α to be |α| ≤ 10 10 cm 2 .…”

Section: Perturbatively Modified Gravitymentioning

confidence: 98%

“…Our approach in [32] and [33] (where α = 0, while β = 0) and in [35] (where β = 0, while α = 0) was different than [34] in two ways: (i) Rather than choosing a fixed specific value for α [32,33] or β [35], we studied its effect, as a free parameter, on the M-R relation and constrained its value by referring to observations, (ii) As the interaction between nucleons can not be neglected, the EoS of ideal neutron gas can not provide realistic M-R relations. We thus employed six different realistic EoS in [32,35] corresponding to a variety of assumptions for the interaction between nucleons rather than the very restrictive EoS of ideal neutron gas.…”

Section: Perturbatively Modified Gravitymentioning

confidence: 99%

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Neutron stars as laboratories for gravity physics

Deliduman¹

2014

AIP Conference Proceedings

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We study the structure of neutron stars in R + αR 2 gravity model with perturbative method. We obtain mass-radius relations for four representative equations of state (EoS). We find that, for |α| ∼ 10 9 cm 2 , the results differ substantially from the results of general relativity. The effects of modified gravity are seen as mimicking a stiff or soft EoS for neutron stars depending upon whether α is negative or positive, respectively. Some of the soft EoS that are excluded within the framework of general relativity can be reconciled for certain values of α of this order with the 2 solar mass neutron star recently observed. Indeed, if the EoS is ever established to be soft, modified gravity of the sort studied here may be required to explain neutron star masses as large as 2 M . The associated length scale √ α ∼ 10 5 cm is of the order of the the typical radius of neutron stars implying that this is the smallest value we could find by using neutron stars as a probe. We thus conclude that the true value of α is most likely much smaller than 10 9 cm 2 .

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Section: Perturbatively Modified Gravitymentioning

confidence: 98%

Section: Perturbatively Modified Gravitymentioning

confidence: 99%

Neutron stars as laboratories for gravity physics

Deliduman¹

2014

AIP Conference Proceedings

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“…Several theoretical approaches for the puzzle have been trying to figure out the problem [3][4][5]. However, other exotic degrees of freedom such as quark matter [6], some unusual condensations of boson-like matter [7], and dark matter [8] are also expected in the core of a neutron star.…”

Section: Introductionmentioning

confidence: 99%

Properties of Neutron Stars with Hyperons and Quarks Using Relativistic Hartree–Fock Approximation and MIT Bag Model

Miyatsu¹,

Cheoun²,

Saito³

2017

Proceedings of the 12th International Conference on Hypernuclear and Strange Particle Physics (HYP2015)

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We study the effect of strangeness on the core of a neutron star. The equation of state for uniform hadronic matter is calculated using the chiral quark-meson coupling model in relativistic Hatree-Fock approach. The MIT bag model with one-gluon-exchange interaction is adopted for a description of quark matter, and the first-order phase transition from hadrons to quarks is assumed under Gibbs criteria for chemical equilibrium. It is found that the maximum mass of a neutron star with hyperons and quarks can support the 2M ⊙ neutron stars due to the Fock contribution, although the quark production softens the EoS. Furthermore, considering the measurements of the massive neutron stars, the strangeness fraction is estimated to be maximally around 14%, and the lower bound of the critical chemical potential of the quark-hadron phase transition turns out to be around 1.4 GeV.

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“…Neutron stars with strong magnetic field in quadratic gravity was considered in [64] for relatively stiff EoS based on model with five meson fields. We consider the quadratic gravity case for EoS based on the above described model.…”

Section: The Cases Of Quadratic and Cubic Curvature Correctionsmentioning

confidence: 99%

Magnetic neutron stars in f(R) gravity

Astashenok

Capozziello

Odintsov

2014

Astrophys Space Sci

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Neutron stars with strong magnetic fields are considered in the framework of f (R) gravity. In order to describe dense matter in magnetic field, the model with baryon octet interacting through σρω-fields is used. The hyperonization process results in softening the equation of state (EoS) and in decreasing the maximal mass. We investigate the effect of strong magnetic field in models involving quadratic and cubic corrections in the Ricci scalar R to the Hilbert-Einstein action. For large fields, the Mass-Radius relation differs considerably from that of General Relativity only for stars with masses close to the maximal one. Another interesting feature is the possible existence of more compact stable stars with extremely large magnetic fields (∼ 6 × 10 18 G instead of ∼ 4 × 10 18G as in General Relativity) in the central regions of the stars. Due to cubic terms, a significant increasing of the maximal mass is possible.

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Possible ambiguities in the equation of state for neutron stars

Cited by 10 publications

References 13 publications

Neutron stars as laboratories for gravity physics

Neutron stars as laboratories for gravity physics

Properties of Neutron Stars with Hyperons and Quarks Using Relativistic Hartree–Fock Approximation and MIT Bag Model

Magnetic neutron stars in f(R) gravity

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