45,828 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
Absence of magnetic long range order in YCrSbO: bond-disorder induced magnetic frustration in a ferromagnetic pyrochlore
The consequences of nonmagnetic-ion dilution for the pyrochlore family
Y()O ( = magnetic ion, = nonmagnetic
ion) have been investigated. As a first step, we experimentally examine the
magnetic properties of YCrSbO ( = 0.5), in which the magnetic
sites (Cr) are percolative. Although the effective Cr-Cr spin exchange
is ferromagnetic, as evidenced by a positive Curie-Weiss temperature,
= 20.1(6) K, our high-resolution neutron powder
diffraction measurements detect no sign of magnetic long range order down to 2
K. In order to understand our observations, we performed numerical simulations
to study the bond-disorder introduced by the ionic size mismatch between
and . Based on these simulations, bond-disorder ( 0.23)
percolates well ahead of site-disorder ( 0.61). This model
successfully reproduces the critical region (0.2 < < 0.25) for the N\'eel
to spin glass phase transition in Zn(CrGa)O, where
the Cr/Ga-sublattice forms the same corner-sharing tetrahedral network as the
-sublattice in Y()O, and the rapid drop in
magnetically ordered moment in the N\'eel phase [Lee , Phys. Rev. B
77, 014405 (2008)]. Our study stresses the nonnegligible role of bond-disorder
on magnetic frustration, even in ferromagnets
Acoustic waves and heating due to molecular energy transfer in an electric discharge CO laser
This paper summarizes analytical studies and the interpretation of experimental results for the compression and rarefaction waves generated in the cavity of a pulsed CO electric discharge laser. A one-dimensional analysis of acoustic waves is applied to a transversely excited laser. The influences of heating in the cathode fall, heat transfer to the cathode, flow through both the anode and cathode, and bulk heating of the plasma are included. The analysis is used to relate the bulk heating rate to observable features of the pressure and density waves. Data obtained from interferograms and reported elsewhere are used to infer the bulk heating rates in a pulsed CO laser. Results are presented for CO/Ar, CO/N2, and N2 plasmas. Comparison of the data with recent theoretical results for the heating due to electron/ neutral collisions and the anharmonic defect associated with V-V energy transfer shows substantial differences at lower values of total energy deposition. The change of heating with E/N is in fairly good agreement with predicted values
Quantum Communication Network Utilizing Quadripartite Entangled States of Optical Field
We propose two types of quantum dense coding communication networks with
optical continuous variables, in which a quadripartite entangled state of the
optical field with totally three-party correlations of quadrature amplitudes is
utilized. In the networks, the exchange of information between any two
participants can be manipulated by one or two of the remaining participants.
The channel capacities for a variety of communication protocols are numerically
calculated. Due to the fact that the quadripartite entangled states applied in
the communication systems have been successfully prepared already in the
laboratory, the proposed schemes are experimentally accessible at present
Resonant Spin Hall Conductance in Two-Dimensional Electron Systems with Rashba Interaction in a Perpendicular Magnetic Field
We study transport properties of a two-dimensional electron system with
Rashba spin-orbit coupling in a perpendicular magnetic field. The spin orbit
coupling competes with Zeeman splitting to introduce additional degeneracies
between different Landau levels at certain magnetic fields. This degeneracy, if
occuring at the Fermi level, gives rise to a resonant spin Hall conductance,
whose height is divergent as 1/T and whose weight is divergent as at
low temperatures. The Hall conductance is unaffected by the Rashba coupling.Comment: 4 pages, 4 figure
Development of high critical current density in multifilamentary round-wire Bi2Sr2CaCu2O8+x by strong overdoping
Bi2Sr2CaCu2O8+x is the only cuprate superconductor that can be made into a
round-wire conductor form with a high enough critical current density Jc for
applications. Here we show that the Jc(5 T,4.2 K) of such Ag-sheathed
filamentary wires can be doubled to more than 1.4x10^5 A/cm^2 by low
temperature oxygenation. Careful analysis shows that the improved performance
is associated with a 12 K reduction in transition temperature Tc to 80 K and a
significant enhancement in intergranular connectivity. In spite of the
macroscopically untextured nature of the wire, overdoping is highly effective
in producing high Jc values.Comment: 4 figure
Optical supercavitation in soft-matter
We investigate theoretically, numerically and experimentally nonlinear
optical waves in an absorbing out-of-equilibrium colloidal material at the
gelification transition. At sufficiently high optical intensity, absorption is
frustrated and light propagates into the medium. The process is mediated by the
formation of a matter-shock wave due to optically induced thermodiffusion, and
largely resembles the mechanism of hydrodynamical supercavitation, as it is
accompanied by a dynamic phase-transition region between the beam and the
absorbing material.Comment: 4 pages, 5 figures, revised version: corrected typos and reference
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