94 research outputs found
Probing primordial features with the primary CMB
CMB photons travel from the last scattering surface, when the primary CMB has
been generated, along the surface of the light cone to us. During their travel,
they are affected by many secondary effects such as the integrated Sachs-Wolfe
effect and CMB lensing. These CMB secondary effects modify the CMB primary
power spectrum adding degeneracies and decreasing the sensibility to primordial
parameters. The possibility to reconstruct the primary CMB anisotropies will
allow us to have a more direct observable to test the physics of the early
universe. We propose to study the imprint of features in the primordial power
spectrum with the primary CMB after the subtraction of the reconstructed ISW
signal from the observed CMB temperature angular power spectrum. We consider
the application to features models able to fit two of the large scales
anomalies observed in the CMB temperature angular power spectrum: the deficit
of power at and at . This method allows to improve
significantly the constraints on the features parameters up to for
models predicting a suppression of power of the quadrupole and up to for
models with features at , assuming instrumental sensitivity
similar to the satellite (depending on the goodness of the ISW
reconstruction). Furthermore, it gives the opportunity to understand if these
anomalies are attributed to early- or late-time physics.Comment: 6 pages, 2 figures, 1 table; Version accepted by Physics of Dark
Univers
CMB and BAO constraints for an induced gravity dark energy model with a quartic potential
We 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 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 at 95% CL with Planck 2013
and BAO data. This is the tightest cosmological constraint on and on
the corresponding derived post-Newtonian parameters. Because of a degeneracy
between and the Hubble constant , we show how larger values for
are allowed, but not preferred at a significant statistical level,
when local measurements of are combined in the analysis with Planck 2013
data.Comment: 13 pages, 7 figure
Cosmological constraints on induced gravity dark energy models
We study induced gravity dark energy models coupled with a simple monomial
potential and a positive exponent . These simple
potentials lead to viable dark energy models with a weak dependence on the
exponent, which characterizes the accelerated expansion of the cosmological
model in the asymptotic attractor, when ordinary matter becomes negligible. We
use recent cosmological data to constrain the coupling 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
2015 data only, we obtain the 95 % CL bound for
, which is further tightened to by adding Baryonic
Acoustic Oscillations (BAO) data. This latter bound improves by % the
limit obtained with the 2013 data and the same compilation of BAO
data. We discuss the dependence of the and on
.Comment: 16 pages, 10 figure
Measuring ISW with next-generation radio surveys
The late-time integrated Sachs-Wolfe (ISW) signal in the CMB temperature
anisotropies is an important probe of dark energy when it can be detected by
cross-correlation with large-scale structure surveys. Because of their huge sky
area, surveys in the radio are well-suited to ISW detection. We show that 21cm
intensity mapping and radio continuum surveys with the SKA in Phase~1 promise a
detection if we use tomography, with a similar forecast for the
precursor EMU survey. In SKA Phase~2, the 21cm galaxy redshift survey and the
continuum survey could deliver a detection. Our analysis of the
radio surveys aims for theoretical accuracy on large scales. Firstly, we
include all the effects on the radio surveys from observing on the past
lightcone: redshift-space distortions and lensing magnification can have a
significant impact on the ISW signal to noise ratio, while Doppler and other
relativistic distortions are not significant. Secondly, we use the full
information in the observable galaxy angular power spectra , by
avoiding the Limber approximation and by including all cross-correlations
between redshift bins in the covariance. Without these cross-bin correlations,
the ISW signal to noise ratio is biased.Comment: 12 pages, 5 figures, 4 tables. Version accepted by MNRA
On the ISW-cluster cross-correlation in future surveys
We investigate the cosmological information contained in the
cross-correlation between the Integrated Sachs-Wolfe (ISW) of the Cosmic
Microwave Background (CMB) anisotropy pattern and galaxy clusters from future
wide surveys. Future surveys will provide cluster catalogues with a number of
objects comparable with galaxy catalogues currently used for the detection of
the ISW signal by cross-correlation with the CMB anisotropy pattern. By
computing the angular power spectra of clusters and the corresponding
cross-correlation with CMB, we perform a signal-to-noise ratio (SNR) analysis
for the ISW detection as expected from the eROSITA and the Euclid space
missions. We discuss the dependence of the SNR of the ISW-cluster
cross-correlation on the specifications of the catalogues and on the reference
cosmology. We forecast that the SNRs for ISW-cluster cross-correlation are
alightly smaller compared to those which can be obtained from future galaxy
surveys but the signal is expected to be detected at high significance, i.e.
more than . We also forecast the joint constraints on parameters
of model extensions of the concordance CDM cosmology by combining CMB
and the ISW-cluster cross-correlation.Comment: 12 pages, 10 figures. Matches version accepted in MNRA
Probing primordial features with the primary CMB
We propose to study the imprint of features in the primordial power spectrum with the primary CMB after the subtraction of the reconstructed ISW signal from the observed CMB temperature angular power spectrum. We consider the application to features models able to fit two of the large scales anomalies observed in the CMB temperature angular power spectrum: the deficit of power at ℓ ∼ 2 and at ℓ ∼ 22.
We show that if the features comes from the primordial power spectrum we should be find consistent constraints of these features model from the CMB temperature angular power spectrum removing or not the late ISW signal. Moreover, this method shows also some improvement on the constraints on
the features parameters up to 16% for models predicting a suppression of power of the quadrupole and
up to 27% for models with features at ℓ ∼ 22, assuming instrumental sensitivity similar to the Planck
satellite (depending on the goodness of the ISW reconstruction). Furthermore, it gives the opportunity to
understand if these anomalies are attributed to early- or late-time physics
Energy-momentum tensor and helicity for gauge fields coupled to a pseudoscalar inflaton
We study the energy-momentum tensor and helicity of gauge fields coupled through to a pseudo-scalar field driving inflation. Under the assumption of a constant time derivative of the background inflaton, we compute analitically divergent and finite terms of the energy density and helicity of gauge fields for any value of the coupling . We introduce a suitable adiabatic expansion for mode functions of physical states of the gauge fields which correctly reproduces ultraviolet divergences in average quantities and identify corresponding counterterms. Our calculations shed light on the accuracy and the range of validity of approximated analytic estimates of the energy density and helicity terms previously existed in the literature in the strongly coupled regime only, i.e. for . We discuss the implications of our analytic calculations for the backreaction of quantum fluctuations onto the inflaton evolution
CMB anisotropies generated by a stochastic background of primordial magnetic fields with non-zero helicity
We 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
ell ~ O(10^3)$.Comment: 25 pages, 30 figure
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