A pitfall of piecewise-polytropic equation of state inference

Raaijmakers, G.; Riley, Thomas E.; Watts, Anna L.

doi:10.1093/mnras/sty1052

Cited by 38 publications

(37 citation statements)

References 68 publications

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“…For example, if two M (R) curves obtained from different equations of state cross, then the inversion is clearly singular at the crossing point. Another difficulty with this approach has been emphasized by Riley et al (2018) and Raaijmakers et al (2018), in the context of EOS models that have separately parameterized segments at different densities, such as models that use a sequence of polytropes. They point out that some neutron stars might not have a central density large enough to reach the highest density in the EOS model.…”

Section: Attempts To Invert Measurements To Obtain the Eosmentioning

confidence: 99%

Constraining the Equation of State of High-density Cold Matter Using Nuclear and Astronomical Measurements

Miller

Chirenti

Lamb

2019

ApJ

126

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The increasing richness of data related to cold dense matter, from laboratory experiments to neutron-star observations, requires a framework for constraining the properties of such matter that makes use of all relevant information. Here, we present a rigorous but practical Bayesian approach that can include diverse evidence, such as nuclear data and the inferred masses, radii, tidal deformabilities, moments of inertia, and gravitational binding energies of neutron stars. We emphasize that the full posterior probability distributions of measurements should be used rather than, as is common, imposing a cut on the maximum mass or other quantities. Our method can be used with any parameterization of the equation of state (EOS). We use both a spectral parameterization and a piecewise polytropic parameterization with variable transition densities to illustrate the implications of current measurements and show how future measurements in many domains could improve our understanding of cold catalyzed matter. We find that different types of measurements will play distinct roles in constraining the EOS in different density ranges. For example, better symmetry energy measurements will have a major influence on our understanding of matter somewhat below nuclear saturation density but little influence above that density. In contrast, precise radius measurements or multiple tidal deformability measurements of the quality of those from GW170817 or better will improve our knowledge of the EOS over a broader density range.

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Section: Attempts To Invert Measurements To Obtain the Eosmentioning

confidence: 99%

Constraining the Equation of State of High-density Cold Matter Using Nuclear and Astronomical Measurements

Miller

Chirenti

Lamb

2019

ApJ

126

View full text Add to dashboard Cite

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“…(See Ref. [27] for a discussion of possible shortcomings of this parametrization when one seeks to determine EoS parameters from a set of measured NS properties. These are of no concern to us in this paper.)…”

Section: A Models For the Nuclear Equation Of Statementioning

confidence: 99%

Trace of the energy-momentum tensor and macroscopic properties of neutron stars

2018

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A generic feature of scalar extensions of general relativity is the coupling of the scalar degrees of freedom to the trace T of the energy-momentum tensor of matter fields. Interesting phenomenology arises when the trace becomes positive-when pressure exceeds one third of the energy density-a condition that may be satisfied in the core of neutron stars. In this work, we study how the positiveness of the trace of the energy-momentum tensor correlates with macroscopic properties of neutron stars. We first show that the compactness for which T = 0 at the stellar center is approximately equation-of-state independent, and given by C = 0.262 +0.011 −0.017 (90% confidence interval). Next, we exploit Bayesian inference to derive a probability distribution function for the value of T at the stellar center given a putative measurement of the compactness of a neutron star. This investigation is a necessary step in order to use present and future observations of neutron star properties to constrain scalar-tensor theories based on effects that depend on the sign of T .

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“…[15] also sought to constrain the NS EOS directly, instead of working exclusively with the tidal deformabilities. It adopted a spectral parameterization for the EOS [34][35][36][37] following methodology originally developed for piecewise polytropes [38][39][40][41]. The spectral coefficients were sampled in place of Λ 1,2 in the waveform, and the most probable EOS was then reconstructed, with error bars, from the first four spectral coefficients.…”

Section: Introductionmentioning

confidence: 99%

Nonparametric inference of the neutron star equation of state from gravitational wave observations

2019

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We develop a non-parametric method for inferring the universal neutron star (NS) equation of state (EOS) from gravitational wave (GW) observations. Many different possible realizations of the EOS are generated with a Gaussian process conditioned on a set of nuclear-theoretic models. These synthetic EOSs are causal and thermodynamically stable by construction, span a broad region of the pressure-density plane, and can be selected to satisfy astrophysical constraints on the NS mass. Associating every synthetic EOS with a pair of component masses M1,2 and calculating the corresponding tidal deformabilities Λ1,2, we perform Monte Carlo integration over the GW likelihood for M1,2 and Λ1,2 to directly infer a posterior process for the NS EOS. We first demonstrate that the method can accurately recover an injected GW signal, and subsequently use it to analyze data from GW170817, finding a canonical deformability of Λ1.4 = 160 +448 −113 and p(2ρnuc) = 1.35 +1.8 −1.2 × 10 34 dyn/cm 2 for the pressure at twice the nuclear saturation density at 90% confidence, in agreement with previous studies, when assuming a loose EOS prior. With a prior more tightly constrained to resemble the theoretical EOS models, we recover Λ1.4 = 556 +163 −172 and p(2ρnuc) = 4.73 +1.4 −2.5 × 10 34 dyn/cm 2 . We further infer the maximum NS mass supported by the EOS to be Mmax = 2.09 +0.37 −0.16(2.04 +0.22 −0.002 ) M with the loose (tight) prior. The Bayes factor between the two priors is B A I 1.12, implying that neither is strongly preferred by the data and suggesting that constraints on the EOS from GW170817 alone may be relatively prior-dominated. *

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A pitfall of piecewise-polytropic equation of state inference

Cited by 38 publications

References 68 publications

Constraining the Equation of State of High-density Cold Matter Using Nuclear and Astronomical Measurements

Constraining the Equation of State of High-density Cold Matter Using Nuclear and Astronomical Measurements

Trace of the energy-momentum tensor and macroscopic properties of neutron stars

Nonparametric inference of the neutron star equation of state from gravitational wave observations

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