22090047
New dark energy constraints from supernovae, microwave background, and galaxy clustering.
Using supernova, cosmic microwave background, and galaxy clustering data, we make the most accurate measurements to date of the dark energy density rho(X) as a function of cosmic time, constraining it in a rather model-independent way, assuming a flat universe. We find that Einstein's simplest scenario, where rho(X)(z) is constant, remains consistent with these new tight constraints and that a big crunch or big rip is more than 50 Gyr away for a broader class of models allowing such cataclysmic events. We discuss popular pitfalls and hidden priors.
15326079
Wavelets and WMAP non-Gaussianity
We study the statistical properties of the first-year Wilkinson Microwave Anisotropy Probe (WMAP) data on different scales using the spherical Mexican hat wavelet transform. Consistent with the 2004 results of Vielva et al., we find a deviation from Gaussianity in the form of kurtosis of wavelet coefficients on 3-4 scales in the southern Galactic hemisphere. This paper extends the work of Vielva et al. as follows: We find that the non-Gaussian signal shows up more strongly in the form of a larger than expected number of cold pixels and also in the form of scale-scale correlations among wavelet coefficients. We establish the robustness of the non-Gaussian signal under more wide-ranging assumptions regarding the Galactic mask applied to the data and the noise statistics. This signal is unlikely to be due to the usual quadratic term parameterized by the nonlinearity parameter fNL. We use the skewness of the spherical Mexican hat wavelet coefficients to constrain fNL with the first-year WMAP data. Our results constrain fNL to be 50+/-80 at 68% confidence and less than 280 at 99% confidence.
11940938
Constraints on generalized extended inflationary models.
We study the physical constraints on generalized extended inflationary theories, in which the Brans-Dicke field {Phi} couples to the inflaton sector in the form of two arbitrary power-law functions of {Phi}. We find that the most stringent constraints arise from the need to suppress large bubbles and from considerations of the density perturbations generated during extended inflation. We find that there are sizable portions of the parameter spaces in which all the constraints are satisfied.
119244043
A robust distance measurement and dark energy constraints from the spherically averaged correlation function of Sloan Digital Sky Survey luminous red Galaxies
We measure the effective distance to z = 0.26, DV (0.26), and mh 2 from the overall shape of the spherically-averaged two-point correlati on function of the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) volume-limited luminous red galaxy (LRG) sample, without assuming a dark energy model or a flat Universe. We giv e the mean and covariance matrix of DV (0.26), mh 2 , bh 2 , and ns. We show that these provide an efficient and accurate summary of the volume-limited LRG data. With flat priors on bh 2 and ns (7σWMAP7), we find mh 2 = 0.131 ± 0.020, and rs/DV (0.26) = 0.1466 +0.0068 0.0073 (the ratio of the sound horizon at the drag epoch to the effective distance to z = 0.26). We find that measurements of mh 2 or m are biased low if flux-limited (instead of volume-limited) L RG sample is used. By scaling the spherically-averaged correlation fun ction, we find the Hubble parameter H(0.26) = 79 +12 13 km s 1 Mpc 1 and the angular diameter distance DA(0.26) = 848 +86 88 Mpc. Combining our results with the cosmic microwave background and supernova data, we obtain k = 0.0059 +0.0092 0.0093 andw = 1.023 +0.054 0.053 (assuming a constant dark energy equation of state). We use LasDamas SDSS mock catalogs to compute the covariance matrix of the correlation function, and investigate the use of lognormal catal ogs as an alternative. We find that the input correlation function can be accurately recovered from lognormal catalogs, although they give larger errors on all scales (especially on small sc ales) compared to the mock catalogs derived from cosmological N-body simulations.
42895334
Dark Energy Search with Supernovae
Abstract To determine the nature of dark energy from observational data, it is important that we use model-independent and optimal methods. We should probe dark energy using its density (allowed to be a free function of cosmic time) instead of its equation of state. We should minimize gravitational lensing effect on supernovae by flux-averaging. We need to include complementary data (for example, from the cosmic microwave background (CMB) and large scale structure (LSS)) in a consistent manner to help break the degeneracy between the dark energy density and the matter density fraction. We should push for ambitious future supernova surveys that can observe a large number of supernovae at the highest possible redshifts. I discuss these and other issues that will be important in our quest to unravel the mystery of the nature of dark energy. Current supernova, CMB, and LSS data already rule out dark energy models with dark energy densities that vary greatly with time; with the cosmological constant model providing an excellent fit to the data. A precise measurement of dark energy density as a free function of cosmic time will have a fundamental impact on particle physics and cosmology.
1842861
Dark Energy Constraints from Baryon Acoustic Oscillations
Baryon acoustic oscillations (BAOs) in the galaxy power spectrum allow us to extract the scale of the comoving sound horizon at recombination, a cosmological standard ruler accurately determined by the cosmic microwave background anisotropy data. We examine various issues important in the use of BAOs to probe dark energy. We find that if we assume a flat universe and priors on ?m, ?mh2, and ?bh2 as expected from the Planck mission, the constraints on dark energy parameters (w0, w') scale much less steeply with survey area than (area)-1/2 for a given redshift range. The constraints on the dark energy density ?X(z), however, do scale roughly with (area)-1/2 due to the strong correlation between H(z) and ?m (which reduces the effect of priors on ?m). Dark energy constraints from BAOs are very sensitive to the assumed linear scale of matter clustering and the redshift accuracy of the survey. For a BAO survey with 0.5 ? z ? 2, ? (R) = 0.4 [corresponding to kmax (z = 0) = 0.086 h Mpc-1], and ?z/ (1 + z) = 0.001, we find = (0.115,0.183) and (0.069, 0.104) for survey areas of 1000 and 10,000 deg2, respectively. We find that it is critical to minimize the bias in the scale estimates in order to derive reliable dark energy constraints. For a 1000 (10,000) deg2 BAO survey, a 1 ? bias in ln H (z) leads to a 2 ? (3 ?) bias in w'. The bias in w' due to the same scale bias from ln DA (z) is slightly smaller and opposite in sign. The results from this paper will be useful in assessing different proposed BAO surveys and guiding the design of optimal dark energy detection strategies.
109237197
Tuning of an rf cavity with a loop inside the cavity
Tuning of an rf cavity with a moving loop inside the cavity is described. The formula to calculate the main parameters ..delta..f and Q of the cavity are given. The results of tests are presented. The advantages of this method are analyzed.
110500799
A fast programmable trigger for pattern recognition
Abstract We have built a fast programmable trigger processor based on a state-of-the-art Field Programmable Gate Array (FPGA) IC for the Palo Verde Neutrino Oscillation Experiment. The trigger processor can accommodate 160 ECL input signals, 8 NIM input signals, 16 ECL output signals and 8 NIM output signals. Our two-level trigger logic is designed asynchronously to maximize speed. We have attained trigger times of 40 ns for level 1 and 100 ns for level 2 with 132 asynchronous inputs. The trigger processor can be upgraded by replacing the FPGA with more advanced versions of the chip as they appear.
118327242
Inhomogeneous and Interacting Vacuum Energy
Vacuum energy is a simple model for dark energy driving an accelerated expansion of the universe. If the vacuum energy is inhomogeneous in spacetime then it must be interacting. We present the general equations for a spacetime-dependent vacuum energy in cosmology, including inhomogeneous perturbations. We show how any dark energy cosmology can be described by an interacting vacuum+matter. Different models for the interaction can lead to different behaviour (e.g., sound speed for dark energy perturbations) and hence could be distinguished by cosmological observations. As an example we present the cosmic microwave microwave background anisotropies and the matter power spectrum for two different versions of a generalised Chaplygin gas cosmology.
117426890
Age spread in galactic star forming region W3 Main
We present near-infrared JHKs imaging as well as K-band multi-object spectroscopy of the massive stellar content of W3 Main using LUCI at the LBT. We confirm 13 OB stars by their absorption line spectra in W3 Main and spectral types between O5V and B4V have been found. Three massive Young Stellar Objects are identified by their emission line spectra and near-infrared excess. From our spectrophotometric analysis of the massive stars and the nature of their surrounding HII regions we derive the evolutionary sequence of W3 Main and we find an age spread of 2–3 Myr.
118465763
Current observational constraints to the holographic dark energy model with a new infrared cutoff via the Markov chain Monte Carlo method
In this paper, the holographic dark energy models with the new infrared cutoff for both the flat case and the nonflat case are confronted with the combined constraints of current cosmological observations: type Ia supernovae, baryon acoustic oscillations, current cosmic microwave background, and the observational Hubble data. By utilizing the Markov chain Monte Carlo method, we obtain the best fit values of the parameters with $1\ensuremath{\sigma}$, $2\ensuremath{\sigma}$ errors in the flat model: ${\ensuremath{\Omega}}_{b}{h}^{2}={0.0233}_{\ensuremath{-}0.0009\ensuremath{-}0.0014}^{+0.0009+0.0013}$, $\ensuremath{\alpha}={0.8502}_{\ensuremath{-}0.0875\ensuremath{-}0.1064}^{+0.0984+0.1299}$, $\ensuremath{\beta}={0.4817}_{\ensuremath{-}0.0773\ensuremath{-}0.0955}^{+0.0842+0.1176}$, ${\ensuremath{\Omega}}_{\mathrm{de}0}={0.7287}_{\ensuremath{-}0.0294\ensuremath{-}0.0429}^{+0.0296+0.0432}$, ${\ensuremath{\Omega}}_{m0}={0.2713}_{\ensuremath{-}0.0296\ensuremath{-}0.0432}^{+0.0294+0.0429}$, ${H}_{0}={66.35}_{\ensuremath{-}2.14\ensuremath{-}3.07}^{+2.38+3.35}$. In the nonflat model, the constraint results are found in $1\ensuremath{\sigma}$, $2\ensuremath{\sigma}$ regions: ${\ensuremath{\Omega}}_{b}{h}^{2}={0.0228}_{\ensuremath{-}0.0010\ensuremath{-}0.0014}^{+0.0010+0.0014}$, ${\ensuremath{\Omega}}_{k}={0.0305}_{\ensuremath{-}0.0134\ensuremath{-}0.0176}^{+0.0092+0.0140}$, $\ensuremath{\alpha}={0.8824}_{\ensuremath{-}0.1163\ensuremath{-}0.1378}^{+0.2180+0.2213}$, $\ensuremath{\beta}={0.5016}_{\ensuremath{-}0.0871\ensuremath{-}0.1102}^{+0.0973+0.1247}$, ${\ensuremath{\Omega}}_{\mathrm{de}0}={0.6934}_{\ensuremath{-}0.0304\ensuremath{-}0.0413}^{+0.0364+0.0495}$, ${\ensuremath{\Omega}}_{m0}={0.2762}_{\ensuremath{-}0.0302\ensuremath{-}0.0412}^{+0.0278+0.0402}$, ${H}_{0}={70.20}_{\ensuremath{-}3.17\ensuremath{-}4.00}^{+3.03+3.58}$. In the best fit holographic dark energy models, the equation of state of dark energy and the deceleration parameter at present are characterized by ${w}_{\mathrm{de}0}=\ensuremath{-}1.1414\ifmmode\pm\else\textpm\fi{}0.0608$, ${q}_{0}=\ensuremath{-}0.7476\ifmmode\pm\else\textpm\fi{}0.0466$ (flat case) and ${w}_{\mathrm{de}0}=\ensuremath{-}1.0653\ifmmode\pm\else\textpm\fi{}0.0661$, ${q}_{0}=\ensuremath{-}0.6231\ifmmode\pm\else\textpm\fi{}0.0569$ (nonflat case). Compared to the $\ensuremath{\Lambda}\mathrm{CDM}$ model, it is found the current combined data sets do not favor the holographic dark energy model over the $\ensuremath{\Lambda}\mathrm{CDM}$ model.