Evidence for quark-matter cores in massive neutron stars

The theory governing the strong nuclear force-quantum chromodynamics-predicts that at sufficiently high energy densities, hadronic nuclear matter undergoes a deconfinement transition to a new phase of quarks and gluons(1). Although this has been observed in ultrarelativistic heavy-ion collisions(2,3), it is currently an open question whether quark matter exists inside neutron stars(4). By combining astrophysical observations and theoretical ab initio calculations in a model-independent way, we find that the inferred properties of matter in the cores of neutron stars with mass corresponding to 1.4 solar masses (M-circle dot) are compatible with nuclear model calculations. However, the matter in the interior of maximally massive stable neutron stars exhibits characteristics of the deconfined phase, which we interpret as evidence for the presence of quark-matter cores. For the heaviest reliably observed neutron stars(5,6) with mass M approximate to 2M(circle dot), the presence of quark matter is found to be linked to the behaviour of the speed of sound c(s) in strongly interacting matter. If the conformal bound cs2Peer reviewe

Neutron star equation of state and tidal deformability with nuclear energy density functionals

Neutron star physics is the ultimate testing place for the physics of dense nuclear matter. Before the detection of gravitational waves from the merger of binary neutron stars, various nuclear equations of state have been used to estimate the macroscopic properties of neutron stars, such as masses and radii, based on electromagnetic observations. However, recent observations of the tidal deformability of neutron star from the gravitational waves GW170817 opened a new era of multi-messenger astronomy and astrophysics, and much theoretical work has been devoted to estimating the tidal deformability of neutron stars. In this article, we review our recent work on the application of nuclear energy density functionals to the properties of neutron stars, including tidal deformability. We found that many nuclear energy density functionals, including the new KIDS (Korea: IBS-Daegu-Sungkyunkwan) model, satisfy constraints both from current electromagnetic and from gravitational-wave observations. We discuss future possibilities of constraining the nuclear matter equation of state from ground-based experiments and multi-messenger observations

A Panel Based Analysis of the Effects of Race/Ethnicity and Other Individual Level Characteristics at Leaving on Returning

Return migration, Tempo of migration, Race/ethnic, Internal migration, Repeat migration,

Finding quark content of neutron stars in light of GW170817

The detection of gravitational waves from GW170817 has provided a new opportunity to constrain the equation of state (EOS) of neutron stars. In this article, we investigate the possible existence of quarks inside the neutron star core in the context of GW170817. The nucleon phase is treated within the relativistic nuclear mean-field approach where we have employed a fully comprehensive set of available models, and the quark phase is described in the Bag model. We show that the nucleonic EOSs which are inconsistent with the tidal deformability bound become consistent when phase transition to quark matter via Gibbs construction is allowed. We find that several nucleonic EOSs support the presence of pure quark matter core with a small mass not more than $$0.17M_\odot$$ confined within a radius of 0.9 km. We also find that the strong correlation between tidal deformability and neutron star radii observed for pure nucleonic stars does persist even with a nucleon-quark phase transition and provides an upper limit on the radius of $$R_{1.4} \lesssim 12.9$$ km for a $$1.4M_\odot$$ neutron star