48,900 research outputs found
A Second Relativistic Mean Field and Virial Equation of State for Astrophysical Simulations
We generate a second equation of state (EOS) of nuclear matter for a wide
range of temperatures, densities, and proton fractions for use in supernovae,
neutron star mergers, and black hole formation simulations. We employ full
relativistic mean field (RMF) calculations for matter at intermediate density
and high density, and the Virial expansion of a non-ideal gas for matter at low
density. For this EOS we use the RMF effective interaction FSUGold, whereas our
earlier EOS was based on the RMF effective interaction NL3. The FSUGold
interaction has a lower pressure at high densities compared to the NL3
interaction. We calculate the resulting EOS at over 100,000 grid points in the
temperature range = 0 to 80 MeV, the density range = 10 to 1.6
fm, and the proton fraction range = 0 to 0.56. We then interpolate
these data points using a suitable scheme to generate a thermodynamically
consistent equation of state table on a finer grid. We discuss differences
between this EOS, our NL3 based EOS, and previous EOSs by Lattimer-Swesty and
H. Shen et al for the thermodynamic properties, composition, and neutron star
structure. The original FSUGold interaction produces an EOS, that we call
FSU1.7, that has a maximum neutron star mass of 1.7 solar masses. A
modification in the high density EOS is introduced to increase the maximum
neutron star mass to 2.1 solar masses and results in a slightly different EOS
that we call FSU2.1. The EOS tables for FSU1.7 and FSU2.1 are available for
download.Comment: updated version according to referee's comments. Phys. Rev. C in
pres
Sensitivity of neutron radii in the sigma_-$ rho_ coupling corrections in relativistic mean field theory
We study the sensitivity of the neutron skin thickness, , in a Pb
nucleus to the addition of nucleon-sigma-rho coupling corrections to a
selection (PK1, NL3, S271, Z271) of interactions in relativistic mean field
model. The PK1 and NL3 effective interactions lead to a minimum value of =
0.16 fm in comparison with the original value of = 0.28 fm. The S271 and
Z271 effective interactions yield even smaller values of = 0.11 fm, which
are similar to those for nonrelativistic mean field models. A precise
measurement of the neutron radius, and therefore , in Pb will place
an important constraint on both relativistic and nonrelativistic mean field
models. We also study the correlation between the radius of a 1.4 solar-mass
neutron star and .Comment: 40 pages 13 figures. to be published in Physical Review
Persistent Decadal-Scale Rainfall Variability in the Tropical South Pacific Convergence Zone Through the Past Six Centuries
Modern Pacific decadal variability (PDV) has global impacts; hence records of PDV from the pre-instrumental period are needed to better inform models that are used to project future climate variability. We focus here on reconstructing rainfall in the western tropical Pacific (Solomon Islands; similar to 9.5 degrees S, similar to 160 degrees E), a region directly influenced by PDV, using cave deposits (stalagmite). A relationship is developed between delta O-18 variations in the stalagmite and local rainfall amount to produce a 600 yr record of rainfall variability from the South Pacific Convergence Zone (SPCZ). We present evidence for large (similar to 1.5 m), abrupt, and periodic changes in total annual rainfall amount on decadal to multidecadal timescales since 1423 +/- 5 CE (Common Era) in the Solomon Islands. The timing of the decadal changes in rainfall inferred from the 20th-century portion of the stalagmite delta O-18 record coincides with previously identified decadal shifts in PDV-related Pacific ocean-atmosphere behavior (Clement et al., 2011; Deser et al., 2004). The Solomons record of PDV is not associated with variations in external forcings, but rather results from internal climate variability. The 600 yr Solomon Islands stalagmite delta O-18 record indicates that decadal oscillations in rainfall are a persistent characteristic of SPCZ-related climate variability.Taiwan ROC NSCNTU 101-2116-M-002-009, 102-2116-M-002-016, 101R7625Geological Science
Theory of single-photon transport in a single-mode waveguide coupled to a cavity containing a two-level atom
The single-photon transport in a single-mode waveguide, coupled to a cavity
embedded with a two-leval atom is analyzed. The single-photon transmission and
reflection amplitudes, as well as the cavity and the atom excitation
amplitudes, are solved exactly via a real-space approach. It is shown that the
dissipation of the cavity and of the atom respectively affects distinctively on
the transport properties of the photons, and on the relative phase between the
excitation amplitudes of the cavity mode and the atom.Comment: 28 pages, 6 figures. Accepted by Physical Review A (2009
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