2,104 research outputs found
Cosmological constraints on neutrino self-interactions with a light mediator
If active neutrinos undergo non-standard (`secret') interactions (NSI)
the cosmological evolution of the neutrino fluid might be altered, leaving an
imprint in cosmological observables. We use the latest publicly available CMB
data from Planck to constrain NSI inducing scattering, under the
assumption that the mediator of the secret interaction is very light. We
find that the effective coupling constant of the interaction, , is constrained at (95\% credible interval), which stregthens to
when Planck non-baseline small-scale
polarization is considered. Our findings imply that after decoupling at
MeV, cosmic neutrinos are free streaming at redshifts , or
if small-scale polarization is included. These bounds are only
marginally improved when data from geometrical expansion probes are included in
the analysis to complement Planck. We also find that the tensions between CMB
and low-redshift measurements of the expansion rate and the amplitude of
matter fluctuations are not significantly reduced. Our results are
independent on the underlying particle physics model as long as is very
light. Considering a model with Majorana neutrinos and a pseudoscalar mediator
we find that the coupling constant of the secret interaction is constrained
at . By further assuming that the pseudoscalar
interaction comes from a dynamical realization of the see-saw mechanism, as in
Majoron models, we can bound the scale of lepton number breaking as
.Comment: V2. Replaced to match version accepted for publication in PRD. Added
more detailed discussion about parameter degeneracies. 14 pages, 6 figures, 3
table
CMB low multipole alignments in the CDM and Dipolar models
The dipolar model \cite{Gordon:2005ai} has attracted much interest because it
may phenomenologically explain the CMB hemispherical power asymmetry found in
the WMAP and Planck data. Since such a model explicitly breaks isotropy at
large angular scales it is natural to wonder whether it can also explain other
CMB directional anomalies. Focusing on the low alignments and assuming
CDM, we confirm that the quadrupole/octupole and the
dipole/quadrupole/octupole alignments are anomalous with a significance up to
C.L., for both WMAP and Planck data. Moreover, we show for the first
time that such features are anomalous also in the dipolar model, roughly at the
same level as in CDM. We conclude that the dipolar model does not
provide a better fit to the data than the CDM.Comment: 13 pages, 2 figures and 4 table
Fast Spherical Harmonic Analysis: a quick algorithm for generating and/or inverting full sky, high resolution CMB Anisotropy maps
We present a fast algorithm for generating full sky, high resolution () simulations of the CMB anisotropy pattern. We also discuss the inverse
problem, that of evaluating from such a map the full set of 's and
the spectral coefficients . We show that using an Equidistant
Cylindrical Projection of the sky substantially speeds up the calculations.
Thus, generating and/or inverting a full sky, high resolution map can be easily
achieved with present day computer technology.Comment: 13 pages, LaTex, 5 PostScript figures included, 1 colour plate
available (PostScript version, 1.6 Mb) at http://itovf2.roma2.infn.it/natoli
CMB Polarization: Scientific Case and Data Analysis Issues
We review the science case for studying CMB polarization. We then discuss the
main issues related to the analysis of forth-coming polarized CMB data, such as
those expected from balloon-borne (e.g. BOOMERanG) and satellite (e.g. Planck)
experiments.Comment: 6 pages, 4 figures. To appear in "Astrophysical Polarized Background"
Workshop Proceedings, eds. S. Cecchini, S. Cortiglioni, R. Sault and C.
Sbarra, AIP, in pres
ROMA: a map-making algorithm for polarised CMB data sets
We present ROMA, a parallel code to produce joint optimal temperature and
polarisation maps out of multidetector CMB observations. ROMA is a fast,
accurate and robust implementation of the iterative generalised least squares
approach to map-making. We benchmark ROMA on realistic simulated data from the
last, polarisation sensitive, flight of BOOMERanG.Comment: Accepted for publication in Astronomy & Astrophysics. Version with
higher quality figures available at http://www.fisica.uniroma2.it/~cosmo/ROM
Pre-Inflationary Relics in the CMB?
String Theory and Supergravity allow, in principle, to follow the transition
of the inflaton from pre-inflationary fast roll to slow roll. This introduces
an infrared depression in the primordial power spectrum that might have left an
imprint in the CMB anisotropy, if it occurred at accessible wavelengths. We
model the effect extending CDM with a scale related to the
infrared depression and explore the constraints allowed by {\sc Planck} data,
employing also more conservative, wider Galactic masks in the low resolution
CMB likelihood. In an extended mask with , we thus find \Delta =
(0.351 \pm 0.114) \times 10^{-3} \, \mbox{Mpc}^{-1}, at confidence
level, to be compared with a nearby value at with the standard
mask. With about 64 --folds of inflation, these values for
would translate into primordial energy scales GeV.Comment: 16 pages, 6 figures, 1 table. Final version to appear in Physics of
the Dark Universe. Contains: more detailed discussion of galactic masking,
improved estimat
The Evens and Odds of CMB Anomalies
The lack of power of large--angle CMB anisotropies is known to increase its
statistical significance at higher Galactic latitudes, where a string--inspired
pre--inflationary scale can also be detected. Considering the Planck
2015 data, and relying largely on a Bayesian approach, we show that the effect
is mostly driven by the \emph{even}-- harmonic multipoles with , which appear sizably suppressed in a way that is robust with
respect to Galactic masking, along with the corresponding detections of
. On the other hand, the first \emph{odd}-- multipoles are only
suppressed at high Galactic latitudes. We investigate this behavior in
different sky masks, constraining through even and odd multipoles, and
we elaborate on possible implications. We include low-- polarization data
which, despite being noise--limited, help in attaining confidence levels of
about 3 in the detection of . We also show by direct forecasts
that a future all--sky --mode cosmic--variance--limited polarization survey
may push the constraining power for beyond 5 .Comment: 49 pages, 19 figures. Figures and final discussion simplified,
references added. Final version to appear in Physics of the Dark Univers
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