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Nontrivial features in the speed of sound inside neutron stars

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arxiv 2309.02345 v2 pith:R6XYEOO6 submitted 2023-09-05 astro-ph.HE gr-qcnucl-th

classification astro-ph.HEgr-qcnucl-th
keywords neutronfeaturesnontrivialphasestarsconstraintscurrentexotic
verification ladder T0 review T1 audit T2 compute T3 formal
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abstract

Measurements of neutron star masses, radii, and tidal deformability have direct connections to nuclear physics via the equation of state (EoS), which for the cold, catalyzed matter in neutron star cores is commonly represented as the pressure as a function of energy density. Microscopic models with exotic degrees of freedom display nontrivial structure in the speed of sound ($c_s$) in the form of first-order phase transitions and bumps, oscillations, and plateaus in the case of crossovers and higher-order phase transitions. We present a procedure based on Gaussian processes to generate an ensemble of EoSs that include nontrivial features. Using a Bayesian analysis incorporating measurements from X-ray sources, gravitational wave observations, and perturbative QCD results, we show that these features are compatible with current constraints. We investigate the possibility of a global maximum in $c_s$ that occurs within the densities realized in neutron stars -- implying a softening of the EoS and possibly an exotic phase in the core of massive stars -- and find that such a global maximum is consistent with, but not required by, current constraints.

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Cited by 5 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Recurring region for neutron-star observables

    astro-ph.HE 2025-06 conditional novelty 6.0 of 10

    Minimizing the average sound speed across a percolation-smoothed deconfinement transition selects hybrid neutron star equations of state that cross a common, small recurring region in mass-radius and mass-tidal deform...

  2. High-Density Sound Speed and Post-Merger Dynamics

    astro-ph.HE 2026-07 conditional novelty 5.0 of 10

    The slope of the high-density sound-speed curve shifts the post-merger gravitational-wave peak frequency and ejecta mass, and that peak frequency partially correlates with an integrated 'intrinsic tidal response' — bu...

  3. A self-consistent Higgs-portal framework for dark matter--admixed neutron stars: Collider-motivated benchmarks meet multimessenger constraints

    astro-ph.HE 2026-07 conditional novelty 5.0 of 10

    Adding heavy dark matter to neutron stars via nχ=FχnB softens the equation of state and lowers the maximum mass, but the vector interaction invoked is numerically negligible.

  4. Microscopic constraints for the equation of state and structure of neutron stars: a Bayesian model mixing framework

    nucl-th 2025-05 conditional novelty 5.0 of 10

    A Bayesian model mixing framework using Gaussian processes extends chiral EFT and pQCD constraints to neutron star matter and demonstrates kernel-dependent equation of state and mass-radius predictions.

  5. Nuclear matter equation of state and astrophysics

    nucl-th 2026-07 conditional

    A review of multimessenger constraints on the neutron-star equation of state, arguing composition remains undetermined and advocating a multidimensional EoS framework and the author-affiliated MUSES software.

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