9,936 research outputs found
Data catalog series for space science and applications flight missions. Volume 3A: Descriptions of low- and medium-altitude scientific spacecraft and investigations
Earth orbits spacecraft whose apogees are well below geostationary altitude and whose primary purpose is to conduct investigations in the near-Earth environment are considered
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
Black Holes with Multiple Charges and the Correspondence Principle
We consider the entropy of near extremal black holes with multiple charges in
the context of the recently proposed correspondence principle of Horowitz and
Polchinski, including black holes with two, three and four Ramond-Ramond
charges. We find that at the matching point the black hole entropy can be
accounted for by massless open strings ending on the D-branes for all cases
except a black hole with four Ramond-Ramond charges, in which case a possible
resolution in terms of brane-antibrane excitations is considered.Comment: 26 pages, harvmac, minor correction
The Vector Analyzing Power in Elastic Electron-Nucleus Scattering
The vector analyzing power A_n is calculated for elastic electron scattering
from a variety of spin zero nuclei at energies from 14 MeV to 3 GeV. Time
reversal symmetry insures that A_n vanish in first Born approximation.
Therefore A_n depends on Coulomb distortions and can be large for scattering
from heavy nuclei. The vector analyzing power is a potential source of
systematic error for parity violation experiments. We find that A_n=-0.361 ppm
for the kinematics of the Parity Radius Experiment (PREX) involving 850 MeV
electrons scattering at six degrees from 208Pb. This is comparable to the
parity violating asymmetry. However for HAPPEX He involving 3 GeV electrons
scattering on 4He we find that A_n is very small.Comment: 6 pages, 6 figures, submitted to Phys. Rev.
Strange matter in the string-flip model
We employ variational Monte Carlo methods to study the transition to strange
matter in a simple one-dimensional string-flip model with two flavors and two
colors of quarks. The dynamics of the system are described in terms of a
many-body potential that confines quarks within hadrons, yet enables the
hadrons to separate without generating unphysical long-range van der Waals
forces. The model has ``natural'' low- and high-density limits: it behaves as a
system of isolated hadrons at low density and as a Fermi gas of quarks at high
density. We show that the system exhibits a transition to strange matter
characterized by an increase in the length-scale for confinement. Yet the small
increase at the transition region --- of only ten percent --- suggests that
clustering correlations remain strong well into the strange-matter domain. Our
results put into question descriptions of strange matter in terms of
noninteracting, or weakly interacting, quarks.Comment: 19 pages, 7 figure
Where is the Information Stored in Black Holes?
It is shown that many modes of the gravitational field exist only inside the
horizon of an extreme black hole in string theory. At least in certain cases,
the number of such modes is sufficient to account for the Bekenstein-Hawking
entropy. These modes are associated with sources which carry Ramond-Ramond
charge, and so may be viewed as the strong coupling limit of D-branes. Although
these sources naturally live at the singularity, they are well defined and
generate modes which extend out to the horizon. This suggests that the
information in an extreme black hole is not localized near the singularity or
the horizon, but extends between them.Comment: 21 pages, reference corrected and comment adde
Black Strings and Classical Hair
We examine the geometry near the event horizon of a family of black string
solutions with traveling waves. It has previously been shown that the metric is
continuous there. Contrary to expectations, we find that the geometry is not
smooth, and the horizon becomes singular whenever a wave is present. Both five
dimensional and six dimensional black strings are considered with similar
results.Comment: 14 pages, harvma
Black Hole Entropy and Superconformal Field Theories on Brane-Antibrane Systems
We obtain the enropy of Schwarzschild and charged black holes in D>4 from
superconformal gases that live on p=10-D dimensional brane-antibrane systems
wrapped on T^p. The preperties of the strongly coupled superconformal theories
such as the appearance of hidden dimensions (for p=1,4) and fractional strings
(for p=5) are crucial for our results. In all cases, the Schwarzschild radius
is given by the transverse fluctuations of the branes and antibranes due to the
finite temperature. We show that our results can be generalized to multicharged
black holes.Comment: 24 pages in phyzzx.te
- âŠ