385 research outputs found
A Selective Bibliography, 1949 - 1965
Kennedy Space Center development from 1949 through 1965 - selected bibliography of article
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
Technologies and techniques offering new interpretations of the landscape evolution
The need for specific documents in terms of environment and landscape has its origin in late eighties, when in Italy both at European and Regional
level several dispositions related to the improvement of the landscape quality came out to guarantee the compatibility of territorial transformations.
Within this traditional context, how innovative, mainly BIM-oriented, technologies can be useful in offering new ways of interpretation for the
landscape planning and safeguarding? The aim of the present work is to read and translate landscape elements using digital BIM-oriented platforms, in order to develop an optimized procedure to collect/organize/implement data and define guidelines for landscape and visual impact assessment; furthermore, the aim is to understand the limits that are still present within available tools. After having read the features of the territory another key point is the creation of digital parametric libraries to represent environmental mitigation works. As far as visual mitigation works are concerned, visibility analysis of the infrastructure is possible through Virtual and Mixed Reality. Once the modeling of specific components is performed, they can be located within the contextual model, where outputs related to the âwholeâ can be extracted and updated afterwards. New digital technologies and techniques undoubtedly offer new interpretation scenarios of the landscape evolution; nevertheless, there are still strong limits related to the interactions among these tools. The present work provides a valid methodology to involve landscape and urban planning in the BIM process. The research also proposes a series of BIM oriented tools and software to develop a typical output (landscape report) required during the design process, useful for landscape architects
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
Work-life interferences in the early academic career stages: The case of precarious researchers in Italy
This paper addresses the topic of workâlife interferences in academic contexts. More specifically, it focuses on early career researchers in the Italian university system. The total availability required from those who work in the research sector is leading to significant transformations of the temporalities of work, especially among the new generation of researchers, whose condition is characterized by a higher degree of instability and uncertainty. Which are the experiences of the early career researchers in an academic context constituted by a growing competition for permanent positions and, as a consequence, by a greatly increased pressure? Which are the main gender differences? In what elements do Science, Technology, Engineering and Mathematics disciplines differ from Social Sciences and Humanities? The collected narratives reveal how the ongoing process of precarization is affecting both the everyday working activities and the private and family lives of early career researchers, with important consequences also on their future prospects
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
f(R) Gravity and its Cosmological Implications
We have investigated the evolution of a homogeneous isotropic background of
the Universe and inhomogeneous subhorizon matter density perturbations in
viable models of present dark energy and cosmic acceleration
analytically and numerically. It is found that viable models generically
exhibit recent crossing of the phantom boundary . Furthermore,
it is shown that the growth index of perturbations depends both on time and
wavenumber. This anomalous growth may explain properties of the observational
matter power spectrum from the SDSS data and can also partially counteract the
spectrum suppression by massive neutrinos making larger values of the total sum
of neutrino rest masses possible.Comment: 10 pages, 8 figures, to be published in the Proceedings of 2nd
International Workshop on Dark Matter, Dark Energy and Matter-Antimatter
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