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Title: Neutron stars and quark matter


Recent observations of neutron star masses close to the maximum predicted by nucleonic equations of state begin to challenge our understanding of dense matter in neutron stars, and constrain the possible presence of quark matter in their deep interiors.

  1. Department of Physics, University of Illinois at Urbana-Champaign, 1110 W. Green Street, Urbana, IL, 61801 (United States)
Publication Date:
OSTI Identifier:
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 892; Journal Issue: 1; Conference: QCHS7: 7. conference on quark confinement and the hadron spectrum, Ponta Delgada, Acores (Portugal), 2-7 Sep 2006; Other Information: DOI: 10.1063/1.2714340; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States

Citation Formats

Baym, Gordon. Neutron stars and quark matter. United States: N. p., 2007. Web. doi:10.1063/1.2714340.
Baym, Gordon. Neutron stars and quark matter. United States. doi:10.1063/1.2714340.
Baym, Gordon. Tue . "Neutron stars and quark matter". United States. doi:10.1063/1.2714340.
title = {Neutron stars and quark matter},
author = {Baym, Gordon},
abstractNote = {Recent observations of neutron star masses close to the maximum predicted by nucleonic equations of state begin to challenge our understanding of dense matter in neutron stars, and constrain the possible presence of quark matter in their deep interiors.},
doi = {10.1063/1.2714340},
journal = {AIP Conference Proceedings},
number = 1,
volume = 892,
place = {United States},
year = {Tue Feb 27 00:00:00 EST 2007},
month = {Tue Feb 27 00:00:00 EST 2007}
  • Assuming a first-order phase transition from nuclear to quark matter in neutron stars and in supernova cores, we have studied the phase transition from two-flavor quark matter to strange matter. This transition has bearing on the cooling of neutron stars and may lead to observable signals in the form of a second neutrino burst. In the case of transition occurring in a supernova core, it has the effect of raising the core temperature and the energy of the shock wave and thus affecting the evolution of the core. In this study we have systematically taken into account the effect ofmore » strong interactions perturbatively to order {alpha}{sub c} and the effect of finite temperature and strange quark mass. {copyright} {ital 1997} {ital The American Astronomical Society}« less
  • The thermal nucleation of quark matter bubbles inside neutron stars is examined for various temperatures which the star may realistically encounter during its lifetime. It is found that for a bag constant less than a critical value a very large part of the star will be converted into the quark phase within a fraction of a second. Depending on the equation of state for neutron star matter and strange quark matter, all or some of the outer parts of the star may subsequently be converted by a slower burning or a detonation.
  • We show that, for physically reasonable bulk and surface properties, the lowest energy state of dense matter consists of quark matter coexisting with nuclear matter in the presence of an essentially uniform background of electrons. We estimate the size and nature of spatial structure in this phase, and show that at the lowest densities the quark matter forms droplets embedded in nuclear matter, whereas at higher densities it can exhibit a variety of different topologies. A finite fraction of the interior of neutron stars could consist of matter in this new phase, which would provide new mechanisms for glitches andmore » cooling.« less
  • A new density dependent effective baryon-baryon interaction has been recently derived from the quark-meson-coupling (QMC) model, offering impressive results in application to finite nuclei and dense baryon matter. This self-consistent, relativistic quark-level approach is used to construct the Equation of State (EoS) and to calculate key properties of high density matter and cold, slowly rotating neutron stars. The results include predictions for the maximum mass of neutron star models, together with the corresponding radius and central density, as well the properties of neutron stars with mass of order 1.4 M{sub {circle_dot}}. The cooling mechanism allowed by the QMC EoS ismore » explored and the parameters relevant to slow rotation, namely the moment of inertia and the period of rotation investigated. The results of the calculation, which are found to be in good agreement with available observational data, are compared with the predictions of more traditional EoS, based on the A18+{delta}v+UIX* and modified Reid soft core potentials, the Skyrme SkM* interaction and two relativistic mean field (RMF) models for a hybrid stars including quark matter. The QMC EoS provides cold neutron star models with maximum mass 1.9-2.1 M{sub {circle_dot}}, with central density less than 6 times nuclear saturation density (n{sub 0} = 0.16 fm{sup -3}) and offers a consistent description of the stellar mass up to this density limit. In contrast with other models, QMC predicts no hyperon contribution at densities lower than 3n{sub 0}, for matter in {beta}-equilibrium. At higher densities, {Xi}{sup -,0} and {Lambda} hyperons are present. The absence of lighter {Sigma}{sup {+-},0} hyperons is understood as a consequence of antisymmetrization, together with the implementation of the color hyperfine interaction in the response of the quark bag to the nuclear scalar field.« less
  • We show that a detailed treatment of the equilibrium composition of a quark liquid is crucial to the structure evaluation of its neutrino emissivity. We demonstrate that when massive s-quarks are present in cold quark matter, the electron fraction Y/sub e/ vanishes above a finite baryon density n/sub ex/. This results in a vanishing total emissivity at high densities, to lowest order in kT. The phase transition at which s-quarks first appear is also studied in detail. The dependences of the composition and emissivity of quark matter on the strange quark mass m/sub s/ and QCD coupling constant (at neutronmore » star densities) ..cap alpha../sub c/ are calculated. If m/sub s/ is small and strange quarks are at least marginally relativistic, the neutrino emissivity of quark matter may be appreciably lower than has been previously calculated. The implications of our results for neutron star cooling calculations are discussed.« less