302 research outputs found
Quantifying Tensions between CMB and Distance Datasets in Models with Free Curvature or Lensing Amplitude
Recent measurements of the Cosmic Microwave Background (CMB) by the Planck
Collaboration have produced arguably the most powerful observational evidence
in support of the standard model of cosmology, i.e. the spatially flat
CDM paradigm. In this work, we perform model selection tests to
examine whether the base CMB temperature and large scale polarization
anisotropy data from Planck 2015 (P15) prefer any of eight commonly used
one-parameter model extensions with respect to flat CDM. We find a
clear preference for models with free curvature, , or free
amplitude of the CMB lensing potential, . We also further develop
statistical tools to measure tension between datasets. We use a Gaussianization
scheme to compute tensions directly from the posterior samples using an
entropy-based method, the surprise, as well as a calibrated evidence ratio
presented here for the first time. We then proceed to investigate the
consistency between the base P15~CMB data and six other CMB and distance
datasets. In flat CDM we find a tension between the base
P15~CMB data and a distance ladder measurement, whereas the former are
consistent with the other datasets. In the curved CDM model we find
significant tensions in most of the cases, arising from the well-known low
power of the low- multipoles of the CMB data. In the flat CDM
model, however, all datasets are consistent with the base
P15~CMB observations except for the CMB lensing measurement, which remains in
significant tension. This tension is driven by the increased power of the CMB
lensing potential derived from the base P15~CMB constraints in both models,
pointing at either potentially unresolved systematic effects or the need for
new physics beyond the standard flat CDM model.Comment: 16 pages, 8 figures, 6 table
On the determination of the deceleration parameter from Supernovae data
Supernovae searches have shown that a simple matter-dominated and
decelerating universe should be ruled out. However a determination of the
present deceleration parameter through a simple kinematical description
is not exempt of possible drawbacks. We show that, with a time dependent
equation of state for the dark energy, a bias is present for : models
which are very far from the so-called Concordance Model can be accommodated by
the data and a simple kinematical analysis can lead to wrong conclusions. We
present a quantitative treatment of this bias and we present our conclusions
when a possible dynamical dark energy is taken into account.Comment: 4 pages, 3 figures, submitte
Nutritive value of different hybrids of sorghum forage determinedin vitro
Eight hybrids of sorghum forage were tested in large plots of two farms in two consecutive years to evaluate their chemical characteristics, nutritive value and yield as a possible substitute for maize silage. Two or three cuts were made depending on climatic conditions. On forage samples taken at ensiling chemical analyses and 24 h gas production were performed, to predict the NEl content. In comparison with maize silage, the sorghum hybrids registered higher protein (13.7% on DM) and NDF (62.6% on DM) contents. Interestingly, the fibre fraction had a low lignin content (3.1% on DM). NEl content ranged from 4.53 to 5.28 MJ/kg DM, the latter for the hybrid with the lowest NDF content. Hybrid effect was significant for ash, NDF, ADF and NEl contents, whilst cut effect was significant for EE, CP, NDF and ADF. Yield was strongly influenced by fertilisation; when the latter was applied, it was in the range of 10-18 t DM, 1.7-2.8 t CP and 47-88 thousand MJ NEl per hectare, as a sum of the 2- 3 cuts. Sorghum forage seems to be a possible alternative to the fibrous maize silage fraction in diets of lactating cows, and an excellent forage for the rations of dry cows and heifers
Cosmology and astrophysics from relaxed galaxy clusters - IV: Robustly calibrating hydrostatic masses with weak lensing
This is the fourth in a series of papers studying the astrophysics and
cosmology of massive, dynamically relaxed galaxy clusters. Here, we use
measurements of weak gravitational lensing from the Weighing the Giants project
to calibrate Chandra X-ray measurements of total mass that rely on the
assumption of hydrostatic equilibrium. This comparison of X-ray and lensing
masses provides a measurement of the combined bias of X-ray hydrostatic masses
due to both astrophysical and instrumental sources. Assuming a fixed cosmology,
and within a characteristic radius (r_2500) determined from the X-ray data, we
measure a lensing to X-ray mass ratio of 0.96 +/- 9% (stat) +/- 9% (sys). We
find no significant trends of this ratio with mass, redshift or the
morphological indicators used to select the sample. In accordance with
predictions from hydro simulations for the most massive, relaxed clusters, our
results disfavor strong, tens-of-percent departures from hydrostatic
equilibrium at these radii. In addition, we find a mean concentration of the
sample measured from lensing data of c_200 = . Anticipated
short-term improvements in lensing systematics, and a modest expansion of the
relaxed lensing sample, can easily increase the measurement precision by
30--50%, leading to similar improvements in cosmological constraints that
employ X-ray hydrostatic mass estimates, such as on Omega_m from the cluster
gas mass fraction.Comment: 13 pages. Submitted to MNRAS. Comments welcom
Prediction of the nutritive value of maize silage using in vitro and near infrared reflectance spectroscopy (NIRS) techniques
Maize silage is by far the most used forage in the diets for dairy cows and beef cattle in a large part of the Po plain, Italy. However, its chemical composition and its nutritive value range widely according to the genotype and to the climatic and agronomic conditions, particularly with regards to the plant maturity at harvest
Combining cluster observables and stacked weak lensing to probe dark energy: Self-calibration of systematic uncertainties
We develop a new method of combining cluster observables (number counts and
cluster-cluster correlation functions) and stacked weak lensing signals of
background galaxy shapes, both of which are available in a wide-field optical
imaging survey. Assuming that the clusters have secure redshift estimates, we
show that the joint experiment enables a self-calibration of important
systematic errors including the source redshift uncertainty and the cluster
mass-observable relation, by adopting a single population of background source
galaxies for the lensing analysis. It allows us to use the relative strengths
of stacked lensing signals at different cluster redshifts for calibrating the
source redshift uncertainty, which in turn leads to accurate measurements of
the mean cluster mass in each bin. In addition, our formulation of stacked
lensing signals in Fourier space simplifies the Fisher matrix calculations, as
well as the marginalization over the cluster off-centering effect, the most
significant uncertainty in stacked lensing. We show that upcoming wide-field
surveys yield stringent constraints on cosmological parameters including dark
energy parameters, without any priors on nuisance parameters that model
systematic uncertainties. Specifically, the stacked lensing information
improves the dark energy FoM by a factor of 4, compared to that from the
cluster observables alone. The primordial non-Gaussianity parameter can also be
constrained with a level of f_NL~10. In this method, the mean source redshift
is well calibrated to an accuracy of 0.1 in redshift, and the mean cluster mass
in each bin to 5-10% accuracies, which demonstrates the success of the
self-calibration of systematic uncertainties from the joint experiment.
(Abridged)Comment: 29 pages, 17 figures, 6 tables, accepted for publication in Phys.
Rev.
The CDM growth rate of structure revisited
We re-examine the growth index of the concordance cosmology in the
light of the latest 6dF and {\em WiggleZ} data. In particular, we investigate
five different models for the growth index , by comparing their
cosmological evolution using observational data of the growth rate of structure
formation at different redshifts. Performing a joint likelihood analysis of the
recent supernovae type Ia data, the Cosmic Microwave Background shift
parameter, Baryonic Acoustic Oscillations and the growth rate data, we
determine the free parameters of the parametrizations and we
statistically quantify their ability to represent the observations. We find
that the addition of the 6dF and {\em WiggleZ} growth data in the likelihood
analysis improves significantly the statistical results. As an example,
considering a constant growth index we find and
.Comment: 8 pages, 5 figures, Accepted for publication by International J. of
Modern Physics D (IJMPD). arXiv admin note: substantial text overlap with
arXiv:1203.672
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