1,346 research outputs found
Testing CDM at the lowest redshifts with SN Ia and galaxy velocities
Peculiar velocities of objects in the nearby universe are correlated due to
the gravitational pull of large-scale structure. By measuring these velocities,
we have a unique opportunity to test the cosmological model at the lowest
redshifts. We perform this test, using current data to constrain the amplitude
of the "signal" covariance matrix describing the velocities and their
correlations. We consider a new, well-calibrated "Supercal" set of low-redshift
SNe Ia as well as a set of distances derived from the fundamental plane
relation of 6dFGS galaxies. Analyzing the SN and galaxy data separately, both
results are consistent with the peculiar velocity signal of our fiducial
CDM model, ruling out the noise-only model with zero peculiar
velocities at greater than (SNe) and (galaxies). When the
two data sets are combined appropriately, the precision of the test increases
slightly, resulting in a constraint on the signal amplitude of , where corresponds to our fiducial model.
Equivalently, we report an 11% measurement of the product of the growth rate
and amplitude of mass fluctuations evaluated at , , valid for our fiducial CDM model.
We explore the robustness of the results to a number of conceivable variations
in the analysis and find that individual variations shift the preferred signal
amplitude by less than . We briefly discuss our Supercal SN Ia
results in comparison with our previous results using the JLA compilation.Comment: 21 pages, 5 figures, minor changes to match the published versio
Effect of Photometric Redshift Uncertainties on Weak Lensing Tomography
We perform a systematic analysis of the effects of photometric redshift
uncertainties on weak lensing tomography. We describe the photo-z distribution
with a bias and Gaussian scatter that are allowed to vary arbitrarily between
intervals of dz = 0.1 in redshift.While the mere presence of bias and scatter
does not substantially degrade dark energy information, uncertainties in both
parameters do. For a fiducial next-generation survey each would need to be
known to better than about 0.003-0.01 in redshift for each interval in order to
lead to less than a factor of 1.5 increase in the dark energy parameter errors.
The more stringent requirement corresponds to a larger dark energy parameter
space, when redshift variation in the equation of state of dark energy is
allowed.Of order 10^4-10^5 galaxies with spectroscopic redshifts fairly sampled
from the source galaxy distribution will be needed to achieve this level of
calibration. If the sample is composed of multiple galaxy types, a fair sample
would be required for each. These requirements increase in stringency for more
ambitious surveys; we quantify such scalings with a convenient fitting formula.
No single aspect of a photometrically binned selection of galaxies such as
their mean or median suffices, indicating that dark energy parameter
determinations are sensitive to the shape and nature of outliers in the photo-z
redshift distribution.Comment: 10 pages, 12 figures, accepted by Ap
Superposition operators on Dirichlet type spaces
We characterize the entire functions ℓfor which the induced nonlinear superposition operator f →ℓof one Besov space Bp into another Bq, where B∞ can be taken to be any of the following natural spaces: VMOA, BMOA, B0, and
B. We do the same for the superpositions from one unweighted Dirichlet-type space Dp into another, and from Bp into the weighted space Dqά. The admissible functions
are typically polynomials whose degree depends on p and q, or entire functions whose order and type are determined by those exponents. We prove some new Trudingertype
inequalities for analytic functions along the way
Food Recalls and Food Safety Perceptions: The September 2006 Spinach Recall Case
This paper examines public perceptions on food safety particularly relating to spinach, which was subject of countrywide recall in 2006. Results indicate that food safety perceptions may be driven by public trust/confidence in institutions whose activities may be directly or indirectly related to food safety. The results further suggest that food safety perceptions may also be related to the type of the product; for example, the public perceives frozen spinach differently from bagged fresh spinach. Additionally, the results show that low levels of objective knowledge about food pathogens and the resulting illnesses have implications on overall food safety. Results further indicate that females and Caucasians perceived the four types of spinach as safe for consumption. This outcome contrasts with views held by young people, people with education below high school and those belonging to the lower incomes groups, who viewed the four types of spinach as unsafe. More attention should be directed toward public education and outreach efforts on overall food safety targeting the youth, low income groups and those with education below high school. In addition, there is need for the regulatory agencies to put their act together, given current low levels of public trust in their role of safeguarding the food supply.Food Consumption/Nutrition/Food Safety,
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