1,295 research outputs found
Detecting a stochastic background of gravitational radiation: Signal processing strategies and sensitivities
We analyze the signal processing required for the optimal detection of a
stochastic background of gravitational radiation using laser interferometric
detectors. Starting with basic assumptions about the statistical properties of
a stochastic gravity-wave background, we derive expressions for the optimal
filter function and signal-to-noise ratio for the cross-correlation of the
outputs of two gravity-wave detectors. Sensitivity levels required for
detection are then calculated. Issues related to: (i) calculating the
signal-to-noise ratio for arbitrarily large stochastic backgrounds, (ii)
performing the data analysis in the presence of nonstationary detector noise,
(iii) combining data from multiple detector pairs to increase the sensitivity
of a stochastic background search, (iv) correlating the outputs of 4 or more
detectors, and (v) allowing for the possibility of correlated noise in the
outputs of two detectors are discussed. We briefly describe a computer
simulation which mimics the generation and detection of a simulated stochastic
gravity-wave signal in the presence of simulated detector noise. Numerous
graphs and tables of numerical data for the five major interferometers
(LIGO-WA, LIGO-LA, VIRGO, GEO-600, and TAMA-300) are also given. The treatment
given in this paper should be accessible to both theorists involved in data
analysis and experimentalists involved in detector design and data acquisition.Comment: 81 pages, 30 postscript figures, REVTE
Dual-energy X-ray absorptiometry scans accurately predict differing body fat content in live sheep
Background
There is considerable interest in implementing mobile scanning technology for on-farm body composition analysis on live animals. These experiments evaluated the use of dual energy X-ray absorptiometry (DXA) as an accurate method of total body fat measurement in live sheep.
Results
In Exp. 1, visceral and whole body fat analysis was undertaken in sheep with body condition scores (BCS) in the range 2 to 3.25 (scale 1: thin to 5: fat). The relationship of BCS was moderately correlated with visceral fat depot mass (r = 0.59, P 0.05, n = 9). There was a moderate correlation between DXA body fat and BCS (r = 0.70, P < 0.01, n = 17), and DXA body fat was highly correlated with chemical body fat (r = 0.81, P < 0.001, n = 9). In Exp. 3, a series of five DXA scans, at 8-week intervals, was performed on growing sheep over a 32-week period. The average BCS ranged from 2.39 ± 0.07 (S.E.M.) to 3.05 ± 0.11 and the DXA body fat (%) ranged from 16.8 ± 0.8 to 24.2 ± 1.2. There was a moderate correlation between DXA body fat and BCS over the 32 weeks (r = 0.61, P < 0.001, n = 24).
Conclusions
Overall, these experiments indicated that there was good agreement between BCS, DXA and chemical analysis for measuring total body fat in sheep, and that DXA scanning is a valid method for longitudinal measurement of total body fat in live sheep
Leptogenesis, neutrino masses and gauge unification
Leptogenesis is considered in its natural context where Majorana neutrinos
fit in a gauge unification scheme and therefore couple to some extra gauge
bosons. The masses of some of these gauge bosons are expected to be similar to
those of the heavy Majorana particles, and this can have important consequences
for leptogenesis. In fact, the effect can go both ways. Stricter bounds are
obtained on one hand due to the dilution of the CP-violating effect by new
decay and scattering channels, while, in a re-heating scheme, the presence of
gauge couplings facilitates the re-population of the Majorana states. The
latter effect allows in particular for smaller Dirac couplings.Comment: 11pages, 7 figures. v2: definition of the lepton asymmetry corrected,
small numerical changes for the baryon number, conclusion does not change;
typos corrected and references adde
Confronting hybrid inflation in supergravity with CMB data
-term GUT inflation coupled to N=1 Supergravity is confronted with CMB
data. Corrections to the string mass-per-unit-length away from the Bogomolny
limit are taken into account. We find that a superpotential coupling
10^{-7}/\mcN \lesssim \kappa \lesssim 10^{-2}/\mcN, with \mcN the dimension
of the Higgs-representation, is still compatible with the data. The parameter
space is enlarged in warm inflation, as well as in the curvaton and
inhomogeneous reheat scenario. -strings formed at the end of -term
inflation are also considered. Because these strings satisfy the Bogomolny
bound the bounds are stronger: the gauge coupling is constrained to the range
.Comment: 36 pages, 15 figure
Genus Topology of the Cosmic Microwave Background from WMAP
We have independently measured the genus topology of the temperature
fluctuations in the cosmic microwave background seen by the Wilkinson Microwave
Anisotropy Probe (WMAP). A genus analysis of the WMAP data indicates
consistency with Gaussian random-phase initial conditions, as predicted by
standard inflation.Comment: PDF: http://www.astro.virginia.edu/~wnc5c/WMAPtopology.pd
Can design documentaries disrupt design for disability?
This paper shows how design documentaries can motivate new perspectives for design and disability. We critically consider the ways in which design documentaries can foreground children's lived experiences and priorities, in cases where it is not always possible to involve children early on in the design process. By presenting a design case for supporting communication that involves children with severe speech and physical impairments and their social peers, we discuss how this narrative method can evoke designer empathy and guide new interpretations. Our findings show that design documentaries can convey to designers rich and multifaceted accounts of children's communication experiences. Although this is found to be generative, we also identify a tension with a bodily impairment understanding of disability. Drawing on reflections from our case study, we propose new methodological implications for embedding design documentaries in the design process of technologies for disability
Fine Features in the Primordial Power Spectrum
A possible origin of the anomalous dip and bump in the primordial power
spectrum, which are reconstructed from WMAP data corresponding to the multipole
by using the inversion method, is investigated as a
consequence of modification of scalar field dynamics in the inflation era.
Utilizing an analytic formula to handle higher order corrections to the
slow-roll approximation, we evaluate the relation between a detailed shape of
inflaton potential and a fine structure in the primordial power spectrum. We
conclude that it is unlikely to generate the observed dip and bump in the power
spectrum by adding any features in the inflaton potential. Though we can make a
fine enough shape in the power spectrum by controlling the feature of the
potential, the amplitude of the dip and bump becomes too small in that case.Comment: 15 pages, 11 figures, submitted to JCA
CMB Power Spectrum from Noncommutative Spacetime
Very recent CMB data of WMAP offers an opportunity to test inflation models,
in particular, the running of spectral index is quite new and can be used to
rule out some models. We show that an noncommutative spacetime inflation model
gives a good explanation of these new results. In fitting the data, we also
obtain a relationship between the noncommutative parameter (string scale) and
the ending time of inflation.Comment: 8 pages, 2 figures; v2: refs. added and minor corrections; v3:
further minor correctio
Moduli Instability in Warped Compactifications of the Type IIB Supergravity
We show that the conifold and deformed-conifold warped compactifications of
the ten-dimensional type IIB supergravity, including the Klebanov-Strassler
solution, are dynamically unstable in the moduli sector representing the scale
of a Calabi-Yau space, although it can be practically stable for a quite long
time in a region with a large warp factor. This instability is associated with
complete supersymmetry breaking except for a special case and produces
significant time-dependence in the structure of the four-dimensional base
spacetime as well as of the internal space.Comment: 24 pages, no figure. Typos corrected, and some arguments in section 5
are adde
- …