101 research outputs found
Phase Transitions in Neutron Stars and Maximum Masses
Using the most recent realistic effective interactions for nuclear matter
with a smooth extrapolation to high densities including causality, we constrain
the equation of state and calculate maximum masses of rotating neutron stars.
First and second order phase transitions to, e.g., quark matter at high
densities are included. If neutron star masses of from
quasi-periodic oscillations in low mass X-ray binaries are confirmed, a soft
equation of state as well as strong phase transitions can be excluded in
neutron star cores.Comment: Replaced with revised version, 7 pages, 3 figs. To appear in Ap. J.
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3P_2-3F_2 pairing in neutron matter with modern nucleon-nucleon potentials
We present results for the pairing gap in neutron matter with
several realistic nucleon-nucleon potentials, in particular with recent,
phase-shift equivalent potentials. We find that their predictions for the gap
cannot be trusted at densities above , where is
the saturation density for symmetric nuclear matter. In order to make
predictions above that density, potential models which fit the nucleon-nucleon
phase shifts up to about 1 GeV are required.Comment: Revtex style, 19 pages, 6 figures inlude
Hyperon effects on the properties of -stable neutron star matter
We present results from Brueckner-Hartree-Fock calculations for
-stable neutron star matter with nucleonic and hyperonic degrees of
freedom employing the most recent parametrizations of the baryon-baryon
interaction of the Nijmegen group. Only and are present up
to densities . The corresponding equations of state are then used
to compute properties of neutron stars such as masses and radii.Comment: 4 pages, contributed talk at HYP2000, Torino, 23-27 Oct. 200
Modern nucleon-nucleon potentials and symmetry energy in infinite matter
We study the symmetry energy in infinite nuclear matter employing a
non-relativistic Brueckner-Hartree-Fock approach and using various new
nucleon-nucleon (NN) potentials, which fit np and pp scattering data very
accurately. The potential models we employ are the recent versions of the
Nijmegen group, Nijm-I, Nijm-II and Reid93, the Argonne potential and
the CD-Bonn potential. All these potentials yield a symmetry energy which
increases with density, resolving a discrepancy that existed for older NN
potentials. The origin of remaining differences is discussed.Comment: 17 pages, 10 figures included, elsevier latex style epsart.st
Relativistic Structure of the Nucleon Self-Energy in Asymmetric Nuclei
The Dirac structure of the nucleon self-energy in asymmetric nuclear matter
cannot reliably be deduced from the momentum dependence of the single-particle
energies. It is demonstrated that such attempts yield an isospin dependence
with even a wrong sign. Relativistic studies of finite nuclei have been based
on such studies of asymmetric nuclear matter. The effects of these isospin
components on the results for finite nuclei are investigated.Comment: 9 pages, Latex 4 figures include
Phaseshift equivalent NN potentials and the deuteron
Different modern phase shift equivalent NN potentials are tested by
evaluating the partial wave decomposition of the kinetic and potential energy
of the deuteron. Significant differences are found, which are traced back to
the matrix elements of the potentials at medium and large momenta. The
influence of the localisation of the one-pion-exchange contribution to these
potentials is analyzed in detail.Comment: 11 pages, LaTeX, 4 figures include
Single particle spectrum and binding energy of nuclear matter
In non-relativistic Brueckner calculations of nuclear matter, the
self-consistent single particle potential is strongly momentum dependent. To
simplify the calculations, a parabolic approximation is often used in the
literature. The variation in the binding energy value introduced by the
parabolic approximation is quantitatively analyzed in detail. It is found that
the approximation can introduce an uncertainty of 1-2 MeV near the saturation
density.Comment: 6 Latex pages, 3 postscript figure
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