Large and massive neutron stars: Implications for the sound speed in dense QCD

Drischler, Christian; Han, Sophia; Reddy, Sanjay

doi:10.48550/arxiv.2110.14896

Cited by 5 publications

(7 citation statements)

References 73 publications

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“…[56,57] study EoS with complex speedof-sound phenomenology, while Refs. [51,[58][59][60][61][62] consider strong first-order phase transitions that result in a discontinuity in the speed of sound and multiple stable branches. The GP prior process is able to recreate such behaviors generically.…”

Section: Discussionmentioning

confidence: 99%

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Implicit correlations within phenomenological parametric models of the neutron star equation of state

2022

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The rapid increase in the number and precision of astrophysical probes of neutron stars in recent years allows for the inference of their equation of state. Observations target different macroscopic properties of neutron stars which vary from star to star, such as mass and radius, but the equation of state allows for a common description of all neutron stars. To connect these observations and infer the properties of dense matter and neutron stars simultaneously, models for the equation of state are introduced. Parametric models rely on carefully engineered functional forms that reproduce a large array of realistic equations of state. Such models benefit from their simplicity but are limited because any finite-parameter model cannot accurately approximate all possible equations of state. Nonparametric methods overcome this by increasing model freedom at the cost of increased complexity. In this study, we compare common parametric and nonparametric models, quantify the limitations of the former, and study the impact of modeling on our current understanding of high-density physics. We show that parametric models impose strongly model-dependent, and sometimes opaque, correlations between density scales. Such interdensity correlations result in tighter constraints that are unsupported by data and can lead to biased inference of the equation of state and of individual neutron star properties.

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Section: Discussionmentioning

confidence: 99%

“…[49]: each point on the line represents a soft lowdensity EoS stitched to an EoS with c 2 s ¼ 1 at different densities. This curve should be interpreted approximately, as the exact causality threshold depends on the details of the low-density EoS [51].…”

Section: Impact Of Eos Model On Current Eos Constraintsmentioning

confidence: 99%

Implicit correlations within phenomenological parametric models of the neutron star equation of state

2022

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“…A meaningful comparison between the regimes probed in BNS mergers and HICs requires a realistic, consistent model for the EOS that is valid across a very large portion of the QCD phase diagram. Such a description should be consistent with constraints from cold compact stars (e.g., [34][35][36][37][38][39][40][41]), properties of symmetric nuclear matter around nuclear saturation density n sat [42][43][44][45][46][47][48][49][50][51][52][53][54][55], as well as large temperature QCD constraints at vanishing and finite density. In the latter case, a consistent description for chiralsymmetry restoration and quark deconfinement must be included to reproduce data from lattice QCD [56][57][58], perturbative QCD [59,60], and high-energy collider experiments [61].…”

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confidence: 70%

Probing neutron-star matter in the lab: connecting binary mergers to heavy-ion collisions

Most¹,

Motornenko²,

Steinheimer³

et al. 2022

Preprint

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As a way to find analogies and differences in the dynamics of hot and dense matter under extreme conditions, we present the first self-consistent relativistic-hydrodynamic calculations of both neutron-star mergers and lowenergy heavy-ion collisions employing the same equation of state. By a direct comparison of the evolution of quantities such as temperature, entropy, and density, we show that neutron-star collision regimes can be probed directly at GSI beam energies. We provide concrete evidence that the physical conditions reached in binary neutron-star mergers can be studied in present and future laboratory experiments, thus bridging 18 orders of magnitude in length scale, from microscopic ion collisions to macroscopic astrophysical compact objects.

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“…[56,57] study EoSs with complex speedof-sound phenomenology, while Refs. [51,[58][59][60][61][62] consider strong first-order phase transitions that result in a discontinuity in the speed-of-sound and multiple stable branches. The GP prior process is able to recreate such behaviors generically.…”

Section: Discussionmentioning

confidence: 99%

“…[49]: each point on the line represents a soft low-density EoS stitched to an EoS with c 2 s = 1 at different densities. This curve should be interpreted approximately, as the exact causality threshold depends on the details of the low-density EoS [51].…”

Section: Impact Of Eos Model On Current Eos Constraintsmentioning

confidence: 99%

Implicit correlations within phenomenological parametric models of the neutron star equation of state

Legred,

Chatziioannou,

Essick

et al. 2022

Preprint

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The rapid increase in the number and precision of astrophysical probes of neutron stars in recent years allows for the inference of their equation of state. Observations target different macroscopic properties of neutron stars which vary from star to star, such as mass and radius, but the equation of state allows for a common description of all neutron stars. To connect these observations and infer the properties of dense matter and neutron stars simultaneously, models for the equation of state are introduced. Parametric models rely on carefully engineered functional forms that reproduce a large array of realistic equations of state. Such models benefit from their simplicity but are limited because any finite-parameter model cannot accurately approximate all possible equations of state. Nonparametric methods overcome this by increasing model freedom at the cost of increased complexity. In this study, we compare common parametric and nonparametric models, quantify the limitations of the former, and study the impact of modeling on our current understanding of high-density physics. We show that parametric models impose strongly model-dependent, and sometimes opaque, correlations between density scales. Such inter-density correlations result in tighter constraints that are unsupported by data and can lead to biased inference of the equation of state and of individual neutron star properties.

show abstract

Large and massive neutron stars: Implications for the sound speed in dense QCD

Abstract: The NASA telescope NICER has recently measured x-ray emissions from the heaviest of the precisely known two-solar mass neutron stars, PSR J0740+6620. Analysis of the data [Miller et al., Astrophys.

Cited by 5 publications

References 73 publications

Implicit correlations within phenomenological parametric models of the neutron star equation of state

Implicit correlations within phenomenological parametric models of the neutron star equation of state

Probing neutron-star matter in the lab: connecting binary mergers to heavy-ion collisions

Implicit correlations within phenomenological parametric models of the neutron star equation of state

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