365 research outputs found
Non-uniform Matter in Neutron Star Crusts Studied by the Variational Method with Thomas-Fermi Calculations
The equation of state (EOS) for neutron star (NS) crusts is studied in the
Thomas-Fermi (TF) approximation using the EOS for uniform nuclear matter
obtained by the variational method with the realistic nuclear Hamiltonian. The
parameters associated with the nuclear three-body force, which are introduced
to describe the saturation properties, are finely adjusted so that the TF
calculations for isolated atomic nuclei reproduce the experimental data on
masses and charge distributions satisfactorily. The resulting root-mean-square
deviation of the masses from the experimental data for mass-measured nuclei is
about 3 MeV. With use of the nuclear EOS thus determined, the nuclei in the
crust of NS at zero temperature are calculated. The predicted proton numbers of
the nuclei in the crust of NS are close to the gross behavior of the results by
Negele and Vautherin, while they are larger than those for the EOS by Shen et
al. due to the difference in the symmetry energy. The density profile of NS is
calculated with the constructed EOS.Comment: 38 pages, 9 figures, accepted for publication in PT
Variational Calculation for the Equation of State of Nuclear Matter at Finite Temperatures
An equation of state (EOS) for uniform nuclear matter is constructed at zero
and finite temperatures with the variational method starting from the realistic
nuclear Hamiltonian composed of the Argonne V18 and UIX potentials. The energy
is evaluated in the two-body cluster approximation with the three-body-force
contribution treated phenomenologically so as to reproduce the empirical
saturation conditions. The obtained energies for symmetric nuclear matter and
neutron matter at zero temperature are in fair agreement with those by Akmal,
Pandharipande and Ravenhall, and the maximum mass of the neutron star is 2.2
Msolar. At finite temperatures, a variational method by Schmidt and
Pandharipande is employed to evaluate the free energy, which is used to derive
various thermodynamic quantities of nuclear matter necessary for supernova
simulations. The result of this variational method at finite temperatures is
found to be self-consistent.Comment: Revised Versio
Search for exotic neutrino-electron interactions using solar neutrinos in XMASS-I
We have searched for exotic neutrino-electron interactions that could be
produced by a neutrino millicharge, by a neutrino magnetic moment, or by dark
photons using solar neutrinos in the XMASS-I liquid xenon detector. We observed
no significant signals in 711 days of data. We obtain an upper limit for
neutrino millicharge of 5.410 at 90\% confidence level
assuming all three species of neutrino have common millicharge. We also set
flavor dependent limits assuming the respective neutrino flavor is the only one
carrying a millicharge, for , for , and for .
These limits are the most stringent yet obtained from direct measurements. We
also obtain an upper limit for the neutrino magnetic moment of
1.810 Bohr magnetons. In addition, we obtain upper limits for
the coupling constant of dark photons in the model of
1.310 if the dark photon mass is 1 MeV,
and 8.810 if it is 10 MeV
First Detection of NaI D lines in High-Redshift Damped Lyman-alpha Systems
A Near-infrared (1.18-1.35 micron) high-resolution spectrum of the
gravitationally-lensed QSO APM 08279+5255 was obtained with the IRCS mounted on
the Subaru Telescope using the AO system. We detected strong NaI D 5891,5897
doublet absorption in high-redshift DLAs at z=1.062 and 1.181, confirming the
presence of NaI, which was first reported for the rest-frame UV NaI
3303.3,3303.9 doublet by Petitjean et al. This is the first detection of NaI D
absorption in a high-redshift (z>1) DLA. In addition, we detected a new NaI
component in the z=1.062 DLA and four new components in the z=1.181 DLA. Using
an empirical relationship between NaI and HI column density, we found that all
"components" have large HI column density, so that each component is classified
as DLA absorption. We also detected strong NaI D absorption associated with a
MgII system at z=1.173. Because no other metal absorption lines were detected
in this system at the velocity of the NaI absorption in previously reported
optical spectra (observed 3.6 years ago), we interpret this NaI absorption
cloud probably appeared in the line of sight toward the QSO after the optical
observation. This newly found cloud is likely to be a DLA based upon its large
estimated HI column density. We found that the N(NaI)/N(CaII) ratios in these
DLAs are systematically smaller than those observed in the Galaxy; they are
more consistent with the ratios seen in the Large Magellanic Cloud. This is
consistent with dust depletion generally being smaller in lower metallicity
environments. However, all five clouds of the z=1.181 system have a high
N(NaI)/N(CaII) ratio, which is characteristic of cold dense gas. We tentatively
suggest that the host galaxy of this system may be the most significant
contributor to the gravitational-lens toward APM 08279+5255.Comment: 22 pages, 6 Postscript figures, 3 tables, ApJ in press (Vol.643, 2
June 2006
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