764 research outputs found
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
Hemispherical power asymmetries in the WMAP 7-year low-resolution temperature and polarization maps
We test the hemispherical power asymmetry of the WMAP 7-year low-resolution
temperature and polarization maps. We consider two natural estimators for such
an asymmetry and exploit our implementation of an optimal angular power
spectrum estimator for all the six CMB spectra. By scanning the whole sky
through a sample of 24 directions, we search for asymmetries in the power
spectra of the two hemispheres, comparing the results with Monte Carlo
simulations drawn from the WMAP 7-year best-fit model. Our analysis extends
previous results to the polarization sector. The level of asymmetry on the ILC
temperature map is found to be compatible with previous results, whereas no
significant asymmetry on the polarized spectra is detected. Moreover, we show
that our results are only weakly affected by the a posteriori choice of the
maximum multipole considered for the analysis. We also forecast the capability
to detect dipole modulation by our methodology at Planck sensitivity.Comment: 7 pages, 9 figures. Accepted for publication in MNRA
A Verilog HDL digital architecture for delay calculation
A method for the calculation of the delay between two digital signals with central frequencies in the range [20, 300] Hz is presented. The method performs a delay calculation in order to determine the bearing angle of a sound source. Computing accuracy is tested against a previous implementation of the Cross Correlation Derivative method. A Verilog RTL model of the method has been tested on a XilinxÂź FPGA in order to evaluate the real performance of the method. Simulations of an ASIC design on a standard CMOS technology predict a power saving of about 25 times per delay stage over previous implementations.Fil: ChacĂłn-RodrĂguez, A.. Universidad de Mar del Plata. Laboratorio de Componentes ElectrĂłnicos; ArgentinaFil: MartĂn-Pirchio, F. N.. Universidad Nacional del Sur. Departamento de IngenierĂa ElĂ©ctrica y de Computadoras; ArgentinaFil: Julian, Pedro Marcelo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - BahĂa Blanca. Instituto de Investigaciones en IngenierĂa ElĂ©ctrica "Alfredo Desages". Universidad Nacional del Sur. Departamento de IngenierĂa ElĂ©ctrica y de Computadoras. Instituto de Investigaciones en IngenierĂa ElĂ©ctrica "Alfredo Desages"; ArgentinaFil: Mandolesi, Pablo Sergio. Universidad Nacional del Sur. Departamento de IngenierĂa ElĂ©ctrica y de Computadoras; Argentin
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