54,736 research outputs found
A Color-Magnitude Diagram for a Globular Cluster In the Giant Elliptical Galaxy NGC 5128
The Hubble Space Telescope has been used to obtain WFPC2 (V,I) photometry for
a large sample of stars in the outer halo of the giant elliptical NGC 5128 (d =
4 Mpc). The globular cluster N5128-C44, at the center of the Planetary Camera
field, is well enough resolved to permit the construction of a color-magnitude
diagram (CMD) for it which covers the brightest two magnitudes of the giant
branch. The CMD is consistent with that of a normal old, moderately
low-metallicity ([Fe/H] = -1.30 globular cluster, distinctly more metal-poor
than most of the field halo stars at the same projected location (which average
[Fe/H] ~ -0.5). This is the most distant globular cluster in which direct
color-magnitude photometry has been achieved to date, and the first one
belonging to a giant E galaxy.Comment: 12 pages, LaTeX, including 5 postscript figures; submitted to
Astronomical Journa
Structural parameters for globular clusters in M31 and generalizations for the fundamental plane
The structures of globular clusters (GCs) reflect their dynamical states and
past histories. High-resolution imaging allows the exploration of morphologies
of clusters in other galaxies. Surface brightness profiles from new Hubble
Space Telescope observations of 34 globular clusters in M31 are presented,
together with fits of several different structural models to each cluster. M31
clusters appear to be adequately fit by standard King models, and do not
obviously require alternate descriptions with relatively stronger halos, such
as are needed to fit many GCs in other nearby galaxies. The derived structural
parameters are combined with corrected versions of those measured in an earlier
survey to construct a comprehensive catalog of structural and dynamical
parameters for M31 GCs with a sample size similar to that for the Milky Way.
Clusters in M31, the Milky Way, Magellanic Clouds, Fornax dwarf spheroidal and
NGC 5128 define a very tight fundamental plane with identical slopes. The
combined evidence for these widely different galaxies strongly reinforces the
view that old globular clusters have near-universal structural properties
regardless of host environment.Comment: AJ in press; 59 pages including 16 figure
Opacity of electromagnetically induced transparency for quantum fluctuations
We analyze the propagation of a pair of quantized fields inside a medium of
three-level atoms in configuration. We calculate the stationary
quadrature noise spectrum of the field after propagating through the medium, in
the case where the probe field is in a squeezed state and the atoms show
electromagnetically induced transparency (EIT). We find an oscillatory transfer
of the initial quantum properties between the probe and pump fields which is
most strongly pronounced when both fields have comparable Rabi frequencies.
This implies that the quantum state measured after propagation can be
completely different from the initial state, even though the mean values of the
field are unaltered
Analytical and experimental investigation of a 1/8-scale dynamic model of the shuttle orbiter. Volume 3A: Supporting data
For abstract, see N75-15681
Analytical and experimental investigation of a 1/8-scale dynamic model of the shuttle orbiter. Volume 1: Summary report
A 1/8-scale structural dynamics model of the space shuttle orbiter was analyzed using the NASA Structural Analysis System (NASTRAN). Comparison of the calculated eigenvalues with preliminary test data for the unrestrained condition indicate that the analytical model was consistently stiffer, being about 20% higher in the first mode. The eigenvectors show reasonably good agreement with test data. A series of analytical and experimental investigations undertaken to resolve the discrepancy are described. Modifications in the NASTRAN model based upon these investigations resulted in close agreement for both eigenvalues and eigenvectors
Susceptibility of the 2D S=1/2 Heisenberg antiferromagnet with an impurity
We use a quantum Monte Carlo method (stochastic series expansion) to study
the effects of a magnetic or nonmagnetic impurity on the magnetic
susceptibility of the two-dimensional Heisenberg antiferromagnet. At low
temperatures, we find a log-divergent contribution to the transverse
susceptibility. We also introduce an effective few-spin model that can
quantitatively capture the differences between magnetic and nonmagnetic
impurities at high and intermediate temperatures.Comment: 5 pages, 4 figures, v2: Updated data in figures, minor changes in
text, v3: Final version, cosmetic change
Effects of surfaces on resistor percolation
We study the effects of surfaces on resistor percolation at the instance of a
semi-infinite geometry. Particularly we are interested in the average
resistance between two connected ports located on the surface. Based on general
grounds as symmetries and relevance we introduce a field theoretic Hamiltonian
for semi-infinite random resistor networks. We show that the surface
contributes to the average resistance only in terms of corrections to scaling.
These corrections are governed by surface resistance exponents. We carry out
renormalization group improved perturbation calculations for the special and
the ordinary transition. We calculate the surface resistance exponents
\phi_{\mathcal S \mathnormal} and \phi_{\mathcal S \mathnormal}^\infty for
the special and the ordinary transition, respectively, to one-loop order.Comment: 19 pages, 3 figure
The Rockefeller Foundation's International Program on Rice Biotechnology
Presents the product of a two-year intensive survey and analysis of the genetic prospects for the world's major food crops conducted in the early 1980s
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