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Title: Kaon condensation and composition of neutron star matter in a modified quark-meson coupling model

Abstract

We use the modified quark-meson coupling (MQMC) model to study the composition profile of neutron star matter and compare the results with those calculated by quantum hadrodynamics (QHD). Both MQMC and QHD model parameters are adjusted to produce exactly the same saturation properties so that we can investigate the model dependences of the matter composition at high densities. We consider the possibility of deep kaon optical potential and find that the composition of matter is very sensitive to the interaction strength of kaons with matter. The onset densities of the kaon condensation are studied in detail by varying the kaon optical potentials. We find that the MQMC model produces the kaon condensation at lower densities than QHD. The presence of kaon condensation changes drastically the population of octet baryons and leptons. Once the kaon condensation takes place, the population of kaons builds up very quickly, and kaons become the dominant component of the matter. We find that the {omega} meson plays an important role in increasing the kaon population and suppressing the hyperon population.

Authors:
;  [1];  [1];  [2];  [3]
  1. Department of Physics and Institute of Basic Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)
  2. (Korea, Republic of)
  3. Department of Physics and Basic Atomic Energy Research Institute, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)
Publication Date:
OSTI Identifier:
20995333
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevC.75.055804; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; COMPARATIVE EVALUATIONS; COUPLING; DENSITY; KAONS; LEPTONS; NEUTRON STARS; NUCLEAR MATTER; OMEGA BARYONS; OPTICAL MODELS; POTENTIALS; QUARK MODEL; QUARKS

Citation Formats

Ryu, C. Y., Kim, B. T., Hyun, C. H., School of Physics, Seoul National University, Seoul 151-742, and Hong, S. W. Kaon condensation and composition of neutron star matter in a modified quark-meson coupling model. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.055804.
Ryu, C. Y., Kim, B. T., Hyun, C. H., School of Physics, Seoul National University, Seoul 151-742, & Hong, S. W. Kaon condensation and composition of neutron star matter in a modified quark-meson coupling model. United States. doi:10.1103/PHYSREVC.75.055804.
Ryu, C. Y., Kim, B. T., Hyun, C. H., School of Physics, Seoul National University, Seoul 151-742, and Hong, S. W. Tue . "Kaon condensation and composition of neutron star matter in a modified quark-meson coupling model". United States. doi:10.1103/PHYSREVC.75.055804.
@article{osti_20995333,
title = {Kaon condensation and composition of neutron star matter in a modified quark-meson coupling model},
author = {Ryu, C. Y. and Kim, B. T. and Hyun, C. H. and School of Physics, Seoul National University, Seoul 151-742 and Hong, S. W.},
abstractNote = {We use the modified quark-meson coupling (MQMC) model to study the composition profile of neutron star matter and compare the results with those calculated by quantum hadrodynamics (QHD). Both MQMC and QHD model parameters are adjusted to produce exactly the same saturation properties so that we can investigate the model dependences of the matter composition at high densities. We consider the possibility of deep kaon optical potential and find that the composition of matter is very sensitive to the interaction strength of kaons with matter. The onset densities of the kaon condensation are studied in detail by varying the kaon optical potentials. We find that the MQMC model produces the kaon condensation at lower densities than QHD. The presence of kaon condensation changes drastically the population of octet baryons and leptons. Once the kaon condensation takes place, the population of kaons builds up very quickly, and kaons become the dominant component of the matter. We find that the {omega} meson plays an important role in increasing the kaon population and suppressing the hyperon population.},
doi = {10.1103/PHYSREVC.75.055804},
journal = {Physical Review. C, Nuclear Physics},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • We study the effects of strong magnetic fields on antikaon condensation in neutron star matter using the quark-meson coupling (QMC) model. The QMC model describes a nuclear many-body system as nonoverlapping MIT bags in which quarks interact through the self-consistent exchange of scalar and vector mesons in the mean-field approximation. It is found that the presence of strong magnetic fields alters the threshold density of antikaon condensation significantly. The onset of K{sup -} condensation stronger depends on the magnetic field strength, and it even shifts beyond the threshold of K{sup 0} condensation for sufficiently strong magnetic fields. In the presencemore » of strong magnetic fields, the equation of state (EOS) becomes stiffer in comparison with the field-free case. The softening of the EOS by antikaon condensation also depends on the magnetic field strength, and it becomes less pronounced with increasing magnetic field strength. The results of the QMC model are compared with those obtained in a relativistic mean-field (RMF) model, and we find there are quantitative differences between the results of the QMC and RMF models.« less
  • The effects of strong magnetic fields on neutron star matter are investigated in the quark-meson coupling (QMC) model. The QMC model describes a nuclear many-body system as nonoverlapping MIT bags in which quarks interact through self-consistent exchange of scalar and vector mesons in the mean-field approximation. The results of the QMC model are compared with those obtained in a relativistic mean-field (RMF) model. It is found that quantitative differences exist between the QMC and RMF models, whereas qualitative trends of the magnetic-field effects on the equation of state and composition of neutron star matter are very similar.
  • The properties of neutron stars, consisting of a crust of hadrons and an internal part of hadrons and kaon condensate, are calculated within the quark-meson-coupling model. We considered stars with nucleons only in the hadron phase and also stars with hyperons as well. The results are compared with the ones obtained from the nonlinear Walecka model for the hadronic phase.
  • The quark-meson coupling model for nuclear matter, which describes nuclear matter as nonoverlapping MIT bags bound by the self-consistent exchange of scalar and vector mesons, is modified by introducing medium modification of the bag constant. We model the density dependence of the bag constant in two different ways: One invokes a direct coupling of the bag constant to the scalar meson field, and the other relates the bag constant to the in-medium nucleon mass. Both models feature a decreasing bag constant with increasing density. We find that when the bag constant is significantly reduced in nuclear medium with respect tomore » its free-space value, large canceling isoscalar Lorentz scalar and vector potentials for the nucleon in nuclear matter emerge naturally. Such potentials are comparable to those suggested by relativistic nuclear phenomenology and finite-density QCD sum rules. This suggests that the reduction of bag constant in nuclear medium may play an important role in low- and medium-energy nuclear physics. {copyright} {ital 1996 The American Physical Society.}« less
  • We study the equation of state of kaon-condensed matter including the effects of temperature and trapped neutrinos. Several different field-theoretical models for the nucleon-nucleon and kaon-nucleon interactions are considered. It is found that the order of the phase transition to a kaon-condensed phase, and whether or not Gibbs' rules for phase equilibrium can be satisfied in the case of a first order transition, depend sensitively on the choice of the kaon-nucleon interaction. To avoid the anomalous high-density behavior of previous models for the kaon-nucleon interaction, a new functional form is developed. For all interactions considered, a first order phase transitionmore » is possible only for magnitudes of the kaon-nucleus optical potential (greater-or-similar sign)100 MeV. The main effect of finite temperature, for any value of the lepton fraction, is to mute the effects of a first order transition, so that the thermodynamics becomes similar to that of a second order transition. Above a critical temperature, found to be at least 30-60 MeV depending upon the interaction, the first order transition disappears. The phase boundaries in baryon density versus lepton number and baryon density versus temperature planes are delineated, which is useful in understanding the outcomes of proto-neutron star simulations. We find that the thermal effects on the maximum gravitational mass of neutron stars are as important as the effects of trapped neutrinos, in contrast to previously studied cases in which the matter contained only nucleons or in which hyperons and/or quark matter were considered. Kaon-condensed equations of state permit the existence of metastable neutron stars, because the maximum mass of an initially hot, lepton-rich proto-neutron star is greater than that of a cold, deleptonized neutron star. The large thermal effects imply that a metastable proto-neutron star's collapse to a black hole could occur much later than in previously studied cases that allow metastable configurations. (c) 2000 The American Physical Society.« less