197 research outputs found
The Case of the Maya Villages of Belize: Reversing the Trend of Government Neglect to Secure Indigenous Land Rights
On the embedding of branes in five-dimensional spaces
We investigate the embedding of four-dimensional branes in five-dimensional
spaces. We firstly consider the case when the embedding space is a vacuum bulk
whose energy-momentum tensor consists of a Dirac delta function with support in
the brane. We then consider the embedding in the context of
Randall-Sundrum-type models, taking into account symmetry and a
cosmological constant. We employ the Campbell-Magaard theorem to construct the
embeddings and are led to the conclusion that the content of energy-matter of
the brane does not necessarily determine its curvature. Finally, as an
application to illustrate our results, we construct the embedding of Minkowski
spacetime filled with dust.Comment: 12 pages - REVTEX To appear in Classical and Quantum Gravit
On Applications of Campbell's Embedding Theorem
A little known theorem due to Campbell is employed to establish the local
embedding of a wide class of 4-dimensional spacetimes in 5-dimensional
Ricci-flat spaces. An embedding for the class of n-dimensional Einstein spaces
is also found. The local nature of Campbell's theorem is highlighted by
studying the embedding of some lower-dimensional spaces.Comment: 17 pages, standard Latex sourc
Perturbations of Dark Matter Gravity
Until recently the study of the gravitational field of dark matter was
primarily concerned with its local effects on the motion of stars in galaxies
and galaxy clusters. On the other hand, the WMAP experiment has shown that the
gravitational field produced by dark matter amplifies the higher acoustic modes
of the CMBR power spectrum, more intensely than the gravitational field of
baryons. Such a wide range of experimental evidences from cosmology to local
gravity suggests the necessity of a comprehensive analysis of the dark matter
gravitational field per se, regardless of any other attributes that dark matter
may eventually possess.
In this paper we introduce and apply Nash's theory of perturbative geometry
to the study of the dark matter gravitational field alone, in a
higher-dimensional framework. It is shown that the dark matter gravitational
perturbations in the early universe can be explained by the extrinsic curvature
of the standard cosmology. Together with the estimated presence of massive
neutrinos, such geometric perturbation is compatible not only with the observed
power spectrum in the WMAP experiment but also with the most recent data on the
accelerated expansion of the universe.
It is possible that the same structure formation exists locally, such as in
the cases of young galaxies or in cluster collisions. In most other cases it
seems to have ceased when the extrinsic curvature becomes negligible, leading
to Einstein's equations in four dimensions. The slow motion of stars in
galaxies and the motion of plasma substructures in nearly colliding clusters
are calculated with the geodesic equation for a slowly moving object in a
gravitational field of arbitrary strength.Comment: 10 pages, 5 figure
Classical tests in brane gravity
The vacuum solutions in brane gravity differ from those in 4D by a number of
additional terms and reduce to the familiar Schwarzschild metric at small
distances. We study the possible roles that such terms may play in the
precession of planetary orbits, bending of light, radar retardation and the
anomaly in mean motion of test bodies. Using the available data from Solar
System experiments, we determine the range of the free parameters associated
with the linear term in the metric. The best results come from the anomalies in
the mean motion of planets. Such studies should shed some light on the origin
of dark energy via the solar system tests.Comment: 10 pages, no figures, to appear in CQ
Support for UNRWA's survival
The United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) provides life-saving humanitarian aid for 5·4 million Palestine refugees now entering their eighth decade of statelessness and conflict. About a third of Palestine refugees still live in 58 recognised camps. UNRWA operates 702 schools and 144 health centres, some of which are affected by the ongoing humanitarian disasters in Syria and the Gaza Strip. It has dramatically reduced the prevalence of infectious diseases, mortality, and illiteracy. Its social services include rebuilding infrastructure and homes that have been destroyed by conflict and providing cash assistance and micro-finance loans for Palestinians whose rights are curtailed and who are denied the right of return to their homeland
The Eighth Data Release of the Sloan Digital Sky Survey: First Data from SDSS-III
The Sloan Digital Sky Survey (SDSS) started a new phase in August 2008, with
new instrumentation and new surveys focused on Galactic structure and chemical
evolution, measurements of the baryon oscillation feature in the clustering of
galaxies and the quasar Ly alpha forest, and a radial velocity search for
planets around ~8000 stars. This paper describes the first data release of
SDSS-III (and the eighth counting from the beginning of the SDSS). The release
includes five-band imaging of roughly 5200 deg^2 in the Southern Galactic Cap,
bringing the total footprint of the SDSS imaging to 14,555 deg^2, or over a
third of the Celestial Sphere. All the imaging data have been reprocessed with
an improved sky-subtraction algorithm and a final, self-consistent photometric
recalibration and flat-field determination. This release also includes all data
from the second phase of the Sloan Extension for Galactic Understanding and
Evolution (SEGUE-2), consisting of spectroscopy of approximately 118,000 stars
at both high and low Galactic latitudes. All the more than half a million
stellar spectra obtained with the SDSS spectrograph have been reprocessed
through an improved stellar parameters pipeline, which has better determination
of metallicity for high metallicity stars.Comment: Astrophysical Journal Supplements, in press (minor updates from
submitted version
The Baryon Oscillation Spectroscopic Survey of SDSS-III
The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the
scale of baryon acoustic oscillations (BAO) in the clustering of matter over a
larger volume than the combined efforts of all previous spectroscopic surveys
of large scale structure. BOSS uses 1.5 million luminous galaxies as faint as
i=19.9 over 10,000 square degrees to measure BAO to redshifts z<0.7.
Observations of neutral hydrogen in the Lyman alpha forest in more than 150,000
quasar spectra (g<22) will constrain BAO over the redshift range 2.15<z<3.5.
Early results from BOSS include the first detection of the large-scale
three-dimensional clustering of the Lyman alpha forest and a strong detection
from the Data Release 9 data set of the BAO in the clustering of massive
galaxies at an effective redshift z = 0.57. We project that BOSS will yield
measurements of the angular diameter distance D_A to an accuracy of 1.0% at
redshifts z=0.3 and z=0.57 and measurements of H(z) to 1.8% and 1.7% at the
same redshifts. Forecasts for Lyman alpha forest constraints predict a
measurement of an overall dilation factor that scales the highly degenerate
D_A(z) and H^{-1}(z) parameters to an accuracy of 1.9% at z~2.5 when the survey
is complete. Here, we provide an overview of the selection of spectroscopic
targets, planning of observations, and analysis of data and data quality of
BOSS.Comment: 49 pages, 16 figures, accepted by A
Gene expression of estrogen receptor-alpha in orbital fibroblasts in Graves’ ophthalmopathy
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