1,981 research outputs found

    Reheating temperature from the CMB

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    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 TRHT_{\text{RH}}. Surprisingly, the obtained equation is independent on the unknown number of relativistic degrees of freedom gg_* produced during the reheating. Based on this equation and the WMAP 7 observations, we find TRH=3.5106T_{\text{RH}}=3.5\cdot 10^6 GeV, which is consistent with the current constraints. The relative uncertainty of the result is, however, very high and equal to σ(TRH)/TRH53\sigma(T_{\text{RH}})/T_{\text{RH}} \approx 53. 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

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    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 Ω1>0\Omega-1 >0, but matches the temperature anisotropy calculated from the standard Ratra-Peebles power spectrum at large ll. 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 adde

    Lincoln Elementary School Needs Assessment Follow-Up: Examining a Community-Based Intervention

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    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

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    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

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    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

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    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 1032 eV1026 eV10^{-32}~{\rm eV} \to 10^{-26}~{\rm eV} compose a fraction <0.01< 0.01 of the cosmological critical density. Here, the sensitivity of a proposed CMB-Stage IV (CMB-S4) experiment (assuming a 1 arcmin beam and <1 μKarcmin< 1~\mu K{\rm-arcmin} 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 10\sim 10 times more sensitive to the ULA energy-density than Planck data alone, across a wide range of ULA masses 1032<ma<1023 eV10^{-32}< m_{a}< 10^{-23}~{\rm eV}, and will probe axion decay constants of fa1016 GeVf_{a}\approx 10^{16}~{\rm GeV}, at the grand unified scale. CMB-S4 could improve the CMB lower bound on the ULA mass from 1025 eV\sim 10^{-25}~{\rm eV} to 1023 eV10^{-23}~{\rm eV}, nearing the mass range probed by dwarf galaxy abundances and dark-matter halo density profiles. These improvements will allow for a multi-σ\sigma 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

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    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 ≥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

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    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 5°C

    The initial conditions of the universe: how much isocurvature is allowed?

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    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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