563 research outputs found
Shadows of Relic Neutrino Masses and Spectra on Highest Energy GZK Cosmic Rays
The Ultra High Energy (UHE) neutrino scattering onto relic cosmic neutrinos
in galactic and local halos offers an unique way to overcome GZK cut-off. The
UHE nu secondary of UHE photo-pion decays may escape the GZK cut-off and travel
on cosmic distances hitting local light relic neutrinos clustered in dark
halos. The Z resonant production and the competitive W^+W^-, ZZ pair production
define a characteristic imprint on hadronic consequent UHECR spectra. This
imprint keeps memory both of the primary UHE nu spectra as well as of the
possible relic neutrino masses values, energy spectra and relic densities. Such
an hadronic showering imprint should reflect into spectra morphology of cosmic
rays near and above GZK 10^{19}-10^{21}eV cut-off energies. A possible neutrino
degenerate masses at eVs or a more complex and significant neutrino mass split
below or near Super-Kamiokande \triangle m_{\nu_{SK}}= 0.1 eV masses might be
reflected after each corresponding Z peak showering, into new twin unexpected
UHECR flux modulation behind GZK energies: E_{p} sim 3(frac{triangle
m_{\nu_{SK}}}/m_{\nu}10^{21}),eV.
Other shadowsof lightest, nearly massless, neutrinos m_{nu_{2K} simeq 0.001eV
simeq kT_{\nu}, their lowest relic temperatures, energies and densities might
be also reflected at even higher energies edges near Grand Unification: E_{p}
\sim 2.2(m_{\nu_{2K}/E_{\nu}})10^{23}, eV .Comment: 14 pages, 6 Figures,Invited Talk Heidelberg DARK 200
Elliptic CMB Sky
The ellipticity of the anisotropy spots of the Cosmic Microwave Background
measured by the Wilkinson Microwave Anisotropy Probe (WMAP) has been studied.
We find an average ellipticity of about 2, confirming with a far larger
statistics similar results found first for the COBE-DMR CMB maps, and then for
the BOOMERanG CMB maps. There are no preferred directions for the obliquity of
the anisotropy spots. The average ellipticity is independent of temperature
threshold and is present on scales both smaller and larger than the horizon at
the last scattering. The measured ellipticity characteristics are consistent
with being the effect of geodesics mixing occurring in an hyperbolic Universe,
and can mark the emergence of CMB ellipticity as a new observable constant
describing the Universe. There is no way of simulating this effect. Therefore
we cannot exclude that the observed behavior of the measured ellipticity can
result from a trivial topology in the popular flat -CDM model, or from
a non-trivial topology.Comment: 10 pages, 5 figures, the version to appear in Mod.Phys.Lett.
WMAP confirming the ellipticity in BOOMERanG and COBE CMB maps
The recent study of BOOMERanG 150 GHz Cosmic Microwave Background (CMB)
radiation maps have detected ellipticity of the temperature anisotropy spots
independent on the temperature threshold. The effect has been found for spots
up to several degrees in size, where the biases of the ellipticity estimator
and of the noise are small. To check the effect, now we have studied, with the
same algorithm and in the same sky region, the WMAP maps. We find ellipticity
of the same average value also in WMAP maps, despite of the different
sensitivity of the two experiments to low multipoles. Large spot elongations
had been detected also for the COBE-DMR maps. If this effect is due to geodesic
mixing and hence due to non precisely zero curvature of the hyperbolic
Universe, it can be linked to the origin of WMAP low multipoles anomaly.Comment: More explanations and two references adde
Is there a common origin for the WMAP low multipole and for the ellipticity in BOOMERanG CMB maps?
We have measured the ellipticity of several degree scale anisotropies in the
BOOMERanG maps of the Cosmic Microwave Background (CMB) at 150 GHz. The average
ellipticity is around 2.6-2.7. The biases of the estimator of the ellipticity
and for the noise are small in this case. Large spot elongation had been
detected also for COBE-DMR maps. If this effect is due to geodesic mixing, it
would indicate a non precisely zero curvature of the Universe which is among
the discussed reasons of the WMAP low multipole anomaly. Both effects are
related to the diameter of the Universe: the geodesics mixing through
hyperbolic geometry, low multipoles through boundary conditions.This common
reason can also be related with the origin of the the cosmological constant:
the modes of vacuum fluctuations conditioned by the boundary conditions lead to
a value of the cosmological constant being in remarkable agreement with the
supernovae observations.Comment: Added: two co-authors and a comment on the possible relation of the
discussed CMB properties with the origin of the observed value of the
cosmological constan
The trispectrum of the Cosmic Microwave Background on sub-degree angular scales: an analysis of the BOOMERanG data
The trispectrum of the cosmic microwave background can be used to assess the
level of non-Gaussianity on cosmological scales. It probes the fourth order
moment, as a function of angular scale, of the probability distribution
function of fluctuations and has been shown to be sensitive to primordial
non-gaussianity, secondary anisotropies (such as the Ostriker-Vishniac effect)
and systematic effects (such as astrophysical foregrounds). In this paper we
develop a formalism for estimating the trispectrum from high resolution sky
maps which incorporates the impact of finite sky coverage. This leads to a
series of operations applied to the data set to minimize the effects of
contamination due to the Gaussian component and correlations between estimates
at different scales. To illustrate the effect of the estimation process, we
apply our procedure to the BOOMERanG data set and show that it is consistent
with Gaussianity. This work presents the first estimation of the CMB
trispectrum on sub-degree scales.Comment: 14 pages, submitted to MNRA
High Order Correction Terms for The Peak-Peak Correlation Function in Nearly-Gaussian Models
One possible way to investigate the nature of the primordial power spectrum
fluctuations is by investigating the statistical properties of the local
maximum in the density fluctuation fields. In this work we present a study of
the mean correlation function, , and the correlation function for high
amplitude fluctuations (the peak-peak correlation) in a slighlty non-Gaussian
context. From the definition of the correlation excess, we compute the Gaussian
two-point correlation function and, using an expansion in Generalized Hermite
polynomials, we estimate the correlation of high density peaks in a
non-Gaussian field with generic distribution and power spectrum. We also apply
the results obtained to a scale-mixed distribution model, which correspond to a
nearly Gaussian model. The results reveal that, even for a small deviation from
Gaussianity, we can expect high density peaks to be much more correlated than
in a Gaussian field with the same power spectrum. In addition, the calculations
reveal how the amplitude of the peaks in the fluctuations field is related to
the existing correlations. Our results may be used as an additional tool to
investigate the behavior of the N-point correlation function, to understand how
non-Gaussian correlations affect the peak-peak statistics and extract more
information about the statistics of the density field.Comment: Accepted for publication in A&
Mapping the CMB Sky: The BOOMERANG experiment
We describe the BOOMERanG experiment, a stratospheric balloon telescope
intended to measure the Cosmic Microwave Background anisotropy at angular
scales between a few degrees and ten arcminutes. The experiment has been
optimized for a long duration (7 to 14 days) flight circumnavigating Antarctica
at the end of 1998. A test flight was performed on Aug.30, 1997 in Texas. The
level of performance achieved in the test flight was satisfactory and
compatible with the requirements for the long duration flight.Comment: 11 pages, 6 figure
Cosmological Parameters from the 2003 flight of BOOMERANG
We present the cosmological parameters from the CMB intensity and
polarization power spectra of the 2003 Antarctic flight of the BOOMERANG
telescope. The BOOMERANG data alone constrains the parameters of the
CDM model remarkably well and is consistent with constraints from a
multi-experiment combined CMB data set. We add LSS data from the 2dF and SDSS
redshift surveys to the combined CMB data set and test several extensions to
the standard model including: running of the spectral index, curvature, tensor
modes, the effect of massive neutrinos, and an effective equation of state for
dark energy. We also include an analysis of constraints to a model which allows
a CDM isocurvature admixture.Comment: 18 pages, 10 figures, submitted to Ap
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