1,722,359 research outputs found
CMB anisotropies generated by a stochastic background of primordial magnetic fields with non-zero helicity
No full textWe consider the impact of a stochastic background of primordial magnetic fields with non-vanishing helicity on CMB anisotropies in temperature and polarization. We compute the exact expressions for the scalar, vector and tensor part of the energy-momentum tensor including the helical contribution, by assuming a power-law dependence for the spectra and a comoving cutoff which mimics the damping due to viscosity. We also compute the parity-odd correlator between the helical and non-helical contribution which generate the TB and EB cross-correlation in the CMB pattern. We finally show the impact of including the helical term on the power spectra of CMB anisotropies up to multipoles with l ∼ (103)
An experimental study of the bond behavior of twisted steel bars embedded in mortar cylinders and in the joints of masonry wallettes
Full text linkAmong the different strengthening techniques available to reinforce masonry buildings, the near-surface mounted technique consists in inserting reinforcing elements of high-strength material in grooves realized by removing part of the mortar in the horizontal bed joints of a masonry wall. The present study deals with two experimental campaigns on pull-out tests conducted on twisted steel bars embedded concentrically in mortar cylinders and in the mortar bed joints of masonry wallettes as in in-situ applications. In order to compare the results between cylindrical and masonry specimens, the same bonded lengths are considered
Role of azelastine nasal spray in the symptomatic treatment of seasonal allergic rhinitis
No full textAdiabatic invariant treatment of a collapsing sphere of quantized dust
No full textThe semiclassical collapse of a sphere of quantized dust is studied. A Born-Oppenheimer decomposition is performed for the wavefunction of the system and the semiclassical limit is considered for the gravitational part. The method of adiabatic invariants for time-dependent Hamiltonians is then employed to find (approximate) solutions to the quantum dust equations of motion. This allows us to obtain corrections to the adiabatic approximation of the dust states associated with the time evolution of the metric. The diverse non-adiabatic corrections are generally associated with particle (dust) creation and related fluctuations. The back-reaction due to the dominant contribution to particle creation is estimated and seen to slow-down the collapse
On the primordial origin of the smoothing excess in the Planck temperature power spectrum in light of LSS data
No full textThe Planck DR3 measurements of the temperature and polarization anisotropies power spectra of the cosmic microwave background (CMB) show an excess of smoothing of the acoustic peaks with respect to ACDM, often quantified by a phenomenological parameter AL. A specific feature superimposed to the primordial power spectrum has been suggested as a physical solution for this smoothing excess. Here, we investigate the impact of this specific localized oscillation with a frequency linear in the wavenumber, designed to mimic the smoothing of CMB temperature spectrum corresponding to AL <^> 1.1-1.2 on the matter power spectrum. We verify the goodness of the predictions in perturbation theory at next-to-leading order with a set of N-body simulations, a necessary step to study the non-linear damping of these primordial oscillations. We show that for a large portion of the parameter space, the amplitude of this primordial oscillation can be strongly damped on the observed nonlinear matter power spectrum at z = 0, but a larger signal is still persistent at z < 2 and is therefore a target for future galaxy surveys at high redshifts. From an analysis of the BOSS DR12 two-point correlation function, we find Alin < 0.26 at 95% CL by keeping the frequency fixed to the best-fit of Planck data
Cosmological constraints on induced gravity dark energy models
No full textWe study induced gravity dark energy models coupled with a simple monomial potential σn and a positive exponent n. These simple potentials lead to viable dark energy models with a weak dependence on the exponent, which characterizes the accelerated expansion in the asymptotic attractor, when ordinary matter becomes negligible. We use recent cosmological data to constrain the coupling γ to the Ricci curvature, under the assumptions that the scalar field starts at rest deep in the radiation era and that the gravitational constant in the Einstein equations is compatible with the one measured in a Cavendish-like experiment. By using P lanck 2015 data only, we obtain the 95 % CL bound γ < 0:0017 for n = 4, which is further tightened to γ < 0:00075 by adding Baryonic Acoustic Oscillations (BAO) data. This latter bound improves by ∼ 30 % the limit obtained with the P lanck 2013 data and the same compilation of BAO data. We discuss the dependence of the γ and GN=GN(z = 0) on n
CMB and BAO constraints for an induced gravity dark energy model with a quartic potential
No full textWe study the predictions for structure formation in an induced gravity dark energy model with a quartic potential. By developing a dedicated Einstein-Boltzmann code, we study self-consistently the dynamics of homogeneous cosmology and of linear perturbations without using any parametrization. By evolving linear perturbations with initial conditions in the radiation era, we accurately recover the quasi-static analytic approximation in the matter dominated era. We use PLANCK 2013 data and a compilation of baryonic acoustic oscillation (BAO) data to constrain the coupling γ to the Ricci curvature and the other cosmological parameters. By connecting the gravitational constant in the Einstein equation to the one measured in a Cavendish-like experiment, we find γ < 0.0012 at 95% CL with PLANCK 2013 and BAO data. This is the tightest cosmological constraint on γ and on the corresponding derived post-Newtonian parameters. Because of a degeneracy between γ and the Hubble constant H0, we show how larger values for γ are allowed, but not preferred at a significant statistical level, when local measurements of H0 are combined in the analysis with PLANCK 2013 data
Testing extended Jordan-Brans-Dicke theories with future cosmological observations
No full textThe extended Jordan-Brans-Dicke (eJBD) theory of gravity is constrained by a host of astrophysical and cosmological observations spanning a wide range of scales. The current cosmological constraints on the first post-Newtonian parameter in these simplest eJBD models in which the recent acceleration of the Universe is connected with the variation of the effective gravitational strength are consistent, but approximately two order of magnitude larger than the time-delay test within the Solar System. We forecast the capabilities of future galaxy surveys in combination with current and future CMB anisotropies measurements to further constrain the simplest dark energy models within eJBD theory of gravity. By considering two cases of a monomial potential (a quartic potential or a cosmological constant), we show how Euclid-like galaxy clustering and weak lensing data in combination with BOSS and future CMB observations have the potential to reach constraints on the first post-Newtonian parameter γPN comparable to those from the Solar System
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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