178 research outputs found
Phenomenological approaches of inflation and their equivalence
In this work, we analyze two possible alternative and model-independent
approaches to describe the inflationary period. The first one assumes a general
equation of state during inflation due to Mukhanov, while the second one is
based on the slow-roll hierarchy suggested by Hoffman and Turner. We find that,
remarkably, the two approaches are equivalent from the observational viewpoint,
as they single out the same areas in the parameter space, and agree with the
inflationary attractors where successful inflation occurs. Rephrased in terms
of the familiar picture of a slowly rolling, canonically normalized scalar
field, the resulting inflaton excursions in these two approaches are almost
identical. Furthermore, once the Galactic dust polarization data from Planck
are included in the numerical fits, inflaton excursions can safely take
sub-Planckian values.Comment: Revtex, 8 pages, 4 figures. References updated. Matches published
version in PR
Probing Gravitational Lensing of the CMB with SDSS-IV Quasars
We study the cross-correlation between the Planck CMB lensing convergence map
and the eBOSS quasar overdensity obtained from the Sloan Digital Sky Survey
(SDSS) IV, in the redshift range . We detect the CMB lensing
convergence-quasar cross power spectrum at significance. The cross
power spectrum provides a quasar clustering bias measurement that is expected
to be particularly robust against systematic effects. The redshift distribution
of the quasar sample has a median redshift , and an effective
redshift about . The best fit bias of the quasar sample is , corresponding to a host halo mass of . This is broadly
consistent with the previous literature on quasars with a similar redshift
range and selection. Since our constraint on the bias comes from the
cross-correlation between quasars and CMB lensing, we expect it to be robust to
a wide range of possible systematic effects that may contaminate the auto
correlation of quasars. We checked for a number of systematic effects from both
CMB lensing and quasar overdensity, and found that all systematics are
consistent with null within . The data is not sensitive to a possible
scale dependence of the bias at present, but we expect that as the number of
quasars increases (in future surveys such as DESI), it is likely that strong
constraints on the scale dependence of the bias can be obtained.Comment: 8 pages, 6 figures, 1 table; matches published version on MNRA
Cosmological limits on neutrino unknowns versus low redshift priors
Recent Cosmic Microwave Background (CMB) temperature and polarization
anisotropy measurements from the Planck mission have significantly improved
previous constraints on the neutrino masses as well as the bounds on extended
models with massless or massive sterile neutrino states. However, due to
parameter degeneracies, additional low redshift priors are mandatory in order
to sharpen the CMB neutrino bounds. We explore here the role of different
priors on low redshift quantities, such as the Hubble constant, the cluster
mass bias, and the reionization optical depth . Concerning current priors
on the Hubble constant and the cluster mass bias, the bounds on the neutrino
parameters may differ appreciably depending on the choices adopted in the
analyses. With regard to future improvements in the priors on the reionization
optical depth, a value of , motivated by astrophysical
estimates of the reionization redshift, would lead to ~eV at
~CL, when combining the full \textit{Planck} measurements, Baryon
Acoustic Oscillation and Planck clusters data, thereby opening the window to
unravel the neutrino mass hierarchy with existing cosmological probes.Comment: 12 pages, 5 figure
Dark Radiation and Inflationary Freedom after Planck 2015
The simplest inflationary models predict a primordial power spectrum (PPS) of
the curvature fluctuations that can be described by a power-law function that
is nearly scale-invariant. It has been shown, however, that the low-multipole
spectrum of the CMB anisotropies may hint the presence of some features in the
shape of the scalar PPS, which could deviate from its canonical power-law form.
We study the possible degeneracies of this non-standard PPS with the neutrino
anisotropies, the neutrino masses, the effective number of relativistic species
and a sterile neutrino or a thermal axion mass. The limits on these additional
parameters are less constraining in a model with a non-standard PPS when only
including the temperature auto-correlation spectrum measurements in the data
analyses. The inclusion of the polarization spectra noticeably helps in
reducing the degeneracies, leading to results that typically show no deviation
from the CDM model with a standard power-law PPS.Comment: 22 pages, 17 figures, 11 tables. Updated to match the published
version. Text abridged upon the referee's request
Constraints on the early and late integrated Sachs-Wolfe effects from the Planck 2015 cosmic microwave background anisotropies in the angular power spectra
The Integrated Sachs-Wolfe (ISW) effect predicts additional anisotropies in the Cosmic MicrowaveBackground due to time variation of the gravitational potential when the expansion of the universeis not matter dominated. The ISW effect is therefore expected in the early universe, due to thepresence of relativistic particles at recombination, and in the late universe, when dark energy startsto dominate the expansion. Deviations from the standard picture can be parameterized byAeISWandAlISW, which rescale the overall amplitude of the early and late ISW effects. Analyzing themost recent CMB temperature spectra from the Planck 2015 release, we detect the presence of theearly ISW at high significance withAeISW= 1.06±0.04 at 68% CL and an upper limit for thelate ISW ofAlISW<1.1 at 95% CL. The inclusion of the recent polarization data from the Planckexperiment erases such 1.5σhint forAeISW6= 1. When considering the recent detections of the lateISW coming from correlations between CMB temperature anisotropies and weak lensing, a value ofAlISW= 0.85±0.21 is predicted at 68% CL, showing a 4σevidence. We discuss the stability of ourresult in the case of an extra relativistic energy component parametrized by the effective neutrinonumberNeffand of a CMB lensing amplitudeA
Relic Neutrinos, thermal axions and cosmology in early 2014
We present up to date cosmological bounds on the sum of active neutrino
masses as well as on extended cosmological scenarios with additional thermal
relics, as thermal axions or sterile neutrino species. Our analyses consider
all the current available cosmological data in the beginning of year 2014,
including the very recent and most precise Baryon Acoustic Oscillation (BAO)
measurements from the Baryon Oscillation Spectroscopic Survey. In the minimal
three active neutrino scenario, we find Sum m_nu < 0.22 eV at 95% CL from the
combination of CMB, BAO and Hubble Space Telescope measurements of the Hubble
constant. A non zero value for the sum of the three active neutrino masses of
about 0.3 eV is significantly favoured at more than 3 standard deviations when
adding the constraints on sigma_8 and Omega_m from the Planck Cluster catalog
on galaxy number counts. This preference for non zero thermal relic masses
disappears almost completely in both the thermal axion and massive sterile
neutrino schemes. Extra light species contribute to the effective number of
relativistic degrees of freedom, parameterised via Neff. We found that when the
recent detection of B mode polarization from the BICEP2 experiment is
considered, an analysis of the combined CMB data in the framework of LCDM+r
models gives Neff=4.00pm0.41, suggesting the presence of an extra relativistic
relic at more than 95 % c.l. from CMB-only data.Comment: 19 pages, 10 figure
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