2,090 research outputs found
Reheating temperature from the CMB
In the recent paper by Mielczarek \emph{et al.} (JCAP {\bf 1007} (2010) 004)
an idea of the method which can be used to put some constraint for the
reheating phase was proposed. Another method of constraining the reheating
temperature has been recently studied by Martin and Ringeval (Phys.\ Rev.\ D
{\bf 82} (2010) 023511). Both methods are based on observations of the cosmic
microwave background (CMB) radiation. In this paper, we develop the idea
introduced in this first article to put constraint on the reheating after the
slow-roll inflation. We restrict our considerations to the case of a massive
inflaton field. The method can be, however, easily extended to the different
inflationary scenarios. As a main result, we derive an expression on the
reheating temperature . Surprisingly, the obtained equation is
independent on the unknown number of relativistic degrees of freedom
produced during the reheating. Based on this equation and the WMAP 7
observations, we find GeV, which is consistent
with the current constraints. The relative uncertainty of the result is,
however, very high and equal to . As we show, this uncertainty will be significantly reduced with future CMB
experiments.Comment: 6 pages, 3 figures. Matches version published in Phys. Rev.
Imprint of spatial curvature on inflation power spectrum
If the universe had a large curvature before inflation there is a deviation
from the scale invariant perturbations of the inflaton at the beginning of
inflation. This may have some effect on the CMB anisotropy at large angular
scales. We calculate the density perturbations for both open and closed
universe cases using the Bunch-Davies vacuum condition on the initial state. We
use our power spectrum to calculate the temperature anisotropy spectrum and
compare the results with the WMAP three year data. We find that our power
spectrum gives a lower quadrupole anisotropy when , but matches
the temperature anisotropy calculated from the standard Ratra-Peebles power
spectrum at large . The determination of spatial curvature from temperature
anisotropy data is not much affected by the different power spectra which arise
from the choice of different boundary conditions for the inflaton perturbation.Comment: 17 pages, 4 figures, revtex4; section on comparison with WMAP3 data
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Lincoln Elementary School Needs Assessment Follow-Up: Examining a Community-Based Intervention
This study explored and expanded a model of community intervention that proposes researcher, practitioner, and community member unification to produce communitywide programs used to improve society. The data were obtained from the community members of Hyrum, Utah, who participated in a needs assessment and then a follow-up survey, which began an examination and refinement process of the city\u27s community programs. Research questions addressed the impact of the community programs in the areas of community safety, cultural relations, and family involvement.
The data suggested that after one year of program implementation, the follow-up study participants perceived a general trend of lowered concern and increased strength within the three areas of study. The results also indicated that although certain programs were utilized by more participants, those programs did not necessarily have the most positive impact on those in the follow-up sample. This study added components of refinement and sensitivity differences to the community intervention model explored
Constraining Isocurvature Initial Conditions with WMAP 3-year data
We present constraints on the presence of isocurvature modes from the
temperature and polarization CMB spectrum data from the WMAP satellite alone,
and in combination with other datasets including SDSS galaxy survey and SNLS
supernovae. We find that the inclusion of polarization data allows the WMAP
data alone, as well as in combination with complementary observations, to place
improved limits on the contribution of CDM and neutrino density isocurvature
components individually. With general correlations, the upper limits on these
sub-dominant isocurvature components are reduced to ~60% of the first year WMAP
results, with specific limits depending on the type of fluctuations. If
multiple isocurvature components are allowed, however, we find that the data
still allow a majority of the initial power to come from isocurvature modes. As
well as providing general constraints we also consider their interpretation in
light of specific theoretical models like the curvaton and double inflation.Comment: 8 pages, 7 figures. Revised Sec 4 and Figs 3-4 post-publication to
correct an error for models with varying isocurvature spectral inde
A new approach to equipment testing
Considerable controversy has arisen during the recent discussions over a new version of the RTCA DO160C/ED 14C Section 22 document at the European Committee for Aviation Electronics. Section 22 is concerned with lightning waveform tests to equipment. Investigations of some of these controversies with circuit analysis and measurements indicate the impedance characteristics required of the transient generators and the possibility of testing to a voltage limit even for current waveforms
Future CMB tests of dark matter: ultra-light axions and massive neutrinos
Measurements of cosmic microwave background (CMB) anisotropies provide strong
evidence for the existence of dark matter and dark energy. They can also test
its composition, probing the energy density and particle mass of different
dark-matter and dark-energy components. CMB data have already shown that
ultra-light axions (ULAs) with mass in the range compose a fraction of the cosmological critical
density. Here, the sensitivity of a proposed CMB-Stage IV (CMB-S4) experiment
(assuming a 1 arcmin beam and noise levels over a sky
fraction of 0.4) to the density of ULAs and other dark-sector components is
assessed. CMB-S4 data should be times more sensitive to the ULA
energy-density than Planck data alone, across a wide range of ULA masses
, and will probe axion decay constants of
, at the grand unified scale. CMB-S4 could
improve the CMB lower bound on the ULA mass from to
, nearing the mass range probed by dwarf galaxy abundances
and dark-matter halo density profiles. These improvements will allow for a
multi- detection of percent-level departures from CDM over a wide range
of masses. Much of this improvement is driven by the effects of weak
gravitational lensing on the CMB, which breaks degeneracies between ULAs and
neutrinos. We also find that the addition of ULA parameters does not
significantly degrade the sensitivity of the CMB to neutrino masses. These
results were obtained using the axionCAMB code (a modification to the CAMB
Boltzmann code), presented here for public use.Comment: 16 pages, 12 figures. The axionCAMB code will be available online at
http://github.com/dgrin1/axionCAMB from 1 August 201
Beyond peer observation of teaching
OBJECTIVE To summarize the evidence on effectiveness of translational diabetes prevention programs, based on promoting lifestyle change to prevent type 2 diabetes in real-world settings and to examine whether adherence to international guideline recommendations is associated with effectiveness. RESEARCH DESIGN AND METHODS Bibliographic databases were searched up to July 2012. Included studies had a follow-up of ā„12 months and outcomes comparing change in body composition, glycemic control, or progression to diabetes. Lifestyle interventions aimed to translate evidence from previous efficacy trials of diabetes prevention into real-world intervention programs. Data were combined using random-effects meta-analysis and meta-regression considering the relationship between intervention effectiveness and adherence to guidelines. RESULTS Twenty-five studies met the inclusion criteria. The primary meta-analysis included 22 studies (24 study groups) with outcome data for weight loss at 12 months. The pooled result of the direct pairwise meta-analysis shows that lifestyle interventions resulted in a mean weight loss of 2.12 kg (95% CI -2.61 to -1.63; I(2) = 91.4%). Adherence to guidelines was significantly associated with a greater weight loss (an increase of 0.3 kg per point increase on a 12-point guideline-adherence scale). CONCLUSIONS Evidence suggests that pragmatic diabetes prevention programs are effective. Effectiveness varies substantially between programs but can be improved by maximizing guideline adherence. However, more research is needed to establish optimal strategies for maximizing both cost-effectiveness and longer-term maintenance of weight loss and diabetes prevention effects
Climate model and proxy data constraints on ocean warming across the Paleocene-Eocene Thermal Maximum
Constraining the greenhouse gas forcing, climatic warming and estimates of climate sensitivity across ancient large transient warming events is a major challenge to the palaeoclimate research community. Here we provide a new compilation and synthesis of the available marine proxy temperature data across the largest of these hyperthermals, the Paleocene-Eocene Thermal Maximum (PETM). This includes the application of consistent temperature calibrations to all data, including the most recent set of calibrations for archaeal lipid-derived palaeothermometry. This compilation provides the basis for an informed discussion of the likely range of PETM warming, the biases present in the existing record and an initial assessment of the geographical pattern of PETM ocean warming. To aid interpretation of the geographic variability of the proxy-derived estimates of PETM warming, we present a comparison of this data with the patterns of warming produced by high pCO2 simulations of Eocene climates using the Hadley Centre atmosphere-ocean general circulation model (AOGCM) HadCM3L. On the basis of this comparison and taking into account the patterns of intermediate-water warming we estimate that the global mean surface temperature anomaly for the PETM is within the range of 4 to 5Ā°C
The initial conditions of the universe: how much isocurvature is allowed?
We investigate the constraints imposed by the current data on correlated
mixtures of adiabatic and non-adiabatic primordial perturbations. We discover
subtle flat directions in parameter space that tolerate large (~60%)
contributions of non-adiabatic fluctuations. In particular, larger values of
the baryon density and a spectral tilt are allowed. The cancellations in the
degenerate directions are explored and the role of priors elucidated.Comment: 4 pages, 4 figures. Submitted to PR
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