3,436 research outputs found
Time-delay and Doppler tests of the Lorentz symmetry of gravity
Modifications to the classic time-delay effect and Doppler shift in General
Relativity (GR) are studied in the context of the Lorentz-violating
Standard-Model Extension (SME). We derive the leading Lorentz-violating
corrections to the time-delay and Doppler shift signals, for a light ray
passing near a massive body. It is demonstrated that anisotropic coefficients
for Lorentz violation control a time-dependent behavior of these signals that
is qualitatively different from the conventional case in GR. Estimates of
sensitivities to gravity-sector coefficients in the SME are given for current
and future experiments, including the recent Cassini solar conjunction
experiment.Comment: 13 pages, 4 figures, references added, matches PRD versio
Water Scarcity and Water Markets: A Comparison of Institutions and Practices in the Murray-Darling Basin of Australia and the Western US
Water markets in Australia’s Murray-Darling Basin (MDB) and the US west are compared in terms of their ability to allocate scarce water resources among competing uses. Both locations have been in the forefront of the development of water markets with defined water rights and conveyance structures to assist in the reallocation of water across competing demands. They also share the challenge of managing water with climate variability and climate change. As these two markets occur in developed, wealthy countries, their experiences in water markets with different water rights (appropriative, riparian and statutory rights) provide ‘best-case’ scenarios of what institutional arrangements work best, indicate which are less effective, and demonstrate what might be possible for greater use of water markets elsewhere in the world. The paper finds that the gains from trade in the MDB is worth hundreds of millions of dollars in per year, total turnover in water rights exceeds 4.3 billion (2008 $) spent or committed by urban buyers between 1987 and 2008. Despite the clear benefits of water markets in both locations, there are on-going restrictions to trade that limit the potential gains and also third-party effects from use that require resolution.
A Comparative Assessment of Water Markets: Insights from the Murray-Darling Basin of Australia and the Western US
Water markets in Australia’s Murray-Darling Basin (MDB) and the US west are compared in terms of their ability to allocate scarce water resources. The study finds that the gains from trade in the MDB are worth hundreds of millions of dollars per year. Total market turnover in water rights exceeds 4.3 billion (2008 $) spent or committed by urban buyers between 1987 and 2008. The two-market comparison suggests that policy attention should be directed towards ways to promote water trade while simultaneously mitigating the legitimate thirdparty concerns about how and where water is used, especially conflicts between consumptive and in situ uses of water. The study finds that institutional innovation is feasible in both countries and that further understanding about the size, duration, and distribution of third-party effects from water trade, and how these effects might be regulated, can improve water markets to better manage water scarcity.water markets, US west, Murray-Darling Basin, gains from trade
Image Deblurring and Near-real-time Atmospheric Seeing Estimation through the Employment of Convergence of Variance
A new image reconstruction algorithm is presented that will remove the effect of atmospheric turbulence on motion compensated frame average images. The primary focus of this research was to develop a blind deconvolution technique that could be employed in a tactical military environment where both time and computational power are limited. Additionally, this technique can be employed to measure atmospheric seeing conditions. In a blind deconvolution fashion, the algorithm simultaneously computes a high resolution image and an average model for the atmospheric blur parameterized by Fried’s seeing parameter. The difference in this approach is that it does not assume a prior distribution for the seeing parameter, rather it assesses the convergence of the image’s variance as the stopping criteria and identification of the proper seeing parameter from a range of candidate values. Experimental results show that the convergence of variance technique allows for estimation of the seeing parameter accurate to within 0.5 cm and often even better depending on the signal to noise ratio
Subtypes of Relapsing-Remitting Multiple Sclerosis Identified by Network Analysis
We used network analysis to identify subtypes of relapsing-remitting multiple sclerosis subjects based on their cumulative signs and symptoms. The electronic medical records of 113 subjects with relapsing-remitting multiple sclerosis were reviewed, signs and symptoms were mapped to classes in a neuro-ontology, and classes were collapsed into sixteen superclasses by subsumption. After normalization and vectorization of the data, bipartite (subject-feature) and unipartite (subject-subject) network graphs were created using NetworkX and visualized in Gephi. Degree and weighted degree were calculated for each node. Graphs were partitioned into communities using the modularity score. Feature maps visualized differences in features by community. Network analysis of the unipartite graph yielded a higher modularity score (0.49) than the bipartite graph (0.25). The bipartite network was partitioned into five communities which were named fatigue, behavioral, hypertonia/weakness, abnormal gait/sphincter, and sensory, based on feature characteristics. The unipartite network was partitioned into five communities which were named fatigue, pain, cognitive, sensory, and gait/weakness/hypertonia based on features. Although we did not identify pure subtypes (e.g., pure motor, pure sensory, etc.) in this cohort of multiple sclerosis subjects, we demonstrated that network analysis could partition these subjects into different subtype communities. Larger datasets and additional partitioning algorithms are needed to confirm these findings and elucidate their significance. This study contributes to the literature investigating subtypes of multiple sclerosis by combining feature reduction by subsumption with network analysis
Classical chaos with Bose-Einstein condensates in tilted optical lattices
A widely accepted definition of ``quantum chaos'' is ``the behavior of a
quantum system whose \emph{classical} \emph{limit is chaotic}''. The dynamics
of quantum-chaotic systems is nevertheless very different from that of their
classical counterparts. A fundamental reason for that is the linearity of
Schr{\"o}dinger equation. In this paper, we study the quantum dynamics of an
ultra-cold quantum degenerate gas in a tilted optical lattice and show that it
displays features very close to \emph{classical} chaos. We show that its phase
space is organized according to the Kolmogorov-Arnold-Moser theorem.Comment: 4 pages, 3 figure
Direct detection of supersymmetric dark matter- Theoretical rates for transitions to excited states
The recent WMAP data have confirmed that exotic dark matter together with the
vacuum energy (cosmological constant) dominate in the flat Universe.
Supersymmetry provides a natural dark matter candidate, the lightest
supersymmetric particle (LSP). Thus the direct dark matter detection is central
to particle physics and cosmology. Most of the research on this issue has
hitherto focused on the detection of the recoiling nucleus. In this paper we
study transitions to the excited states, focusing on the first excited state at
50 keV of Iodine A=127. We find that the transition rate to this excited state
is about 10 percent of the transition to the ground state. So, in principle,
the extra signature of the gammai ray following its de-excitation can be
exploited experimentally.Comment: LaTex, 13 pages, 3 postscript figures, 1 table, to appear in IJMP
The Fornax Spectroscopic Survey: The Number of Unresolved Compact Galaxies
We describe a sample of thirteen bright (18.5<Bj<20.1) compact galaxies at
low redshift (0.05<z<0.21) behind the Fornax Cluster. These galaxies are
unresolved on UK Schmidt sky survey plates, so would be missing from most
galaxy catalogs compiled from this material. The objects were found during
initial observations of The Fornax Spectroscopic Survey. This project is using
the Two-degree Field spectrograph on the Anglo-Australian Telescope to obtain
spectra for a complete sample of all 14000 objects, stellar and non-stellar,
with 16.5<Bj<19.7, in a 12 square degree area centered on the Fornax cluster of
galaxies. The surface density of compact galaxies with magnitudes 16.5<Bj<19.7
is 7+/-3 /sq.deg., representing 2.8+/-1.6% of all local (z<0.2) galaxies to
this limit. There are 12+/-3 /sq.deg. with 16.5<Bj<20.2. They are luminous
(-21.5<Mb<-18.0, for H0=50 km/s/mpc) and most have strong emission lines (H
alpha equivalent widths of 40-200 A) and small sizes typical of luminous HII
galaxies and compact narrow emission line galaxies. Four out of thirteen have
red colors and early-type spectra, so are unlikely to have been detected in any
previous surveys.Comment: LaTeX source; 5 pages including 3 figures; uses emulateapj.st
Signals for Lorentz Violation in Post-Newtonian Gravity
The pure-gravity sector of the minimal Standard-Model Extension is studied in
the limit of Riemann spacetime. A method is developed to extract the modified
Einstein field equations in the limit of small metric fluctuations about the
Minkowski vacuum, while allowing for the dynamics of the 20 independent
coefficients for Lorentz violation. The linearized effective equations are
solved to obtain the post-newtonian metric. The corresponding post-newtonian
behavior of a perfect fluid is studied and applied to the gravitating many-body
system. Illustrative examples of the methodology are provided using bumblebee
models. The implications of the general theoretical results are studied for a
variety of existing and proposed gravitational experiments, including lunar and
satellite laser ranging, laboratory experiments with gravimeters and torsion
pendula, measurements of the spin precession of orbiting gyroscopes, timing
studies of signals from binary pulsars, and the classic tests involving the
perihelion precession and the time delay of light. For each type of experiment
considered, estimates of the attainable sensitivities are provided. Numerous
effects of local Lorentz violation can be studied in existing or near-future
experiments at sensitivities ranging from parts in 10^4 down to parts in
10^{15}.Comment: 46 pages two-column REVTeX, accepted in Physical Review
Global musical diversity is largely independent of linguistic and genetic histories
Music is a universal yet diverse cultural trait transmitted between generations. The extent to which global musical diversity traces cultural and demographic history, however, is unresolved. Using a global musical dataset of 5242 songs from 719 societies, we identify five axes of musical diversity and show that music contains geographical and historical structures analogous to linguistic and genetic diversity. After creating a matched dataset of musical, genetic, and linguistic data spanning 121 societies containing 981 songs, 1296 individual genetic profiles, and 121 languages, we show that global musical similarities are only weakly and inconsistently related to linguistic or genetic histories, with some regional exceptions such as within Southeast Asia and sub-Saharan Africa. Our results suggest that global musical traditions are largely distinct from some non-musical aspects of human history
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