886 research outputs found
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
A semi-coherent analysis method to search for continuous gravitational waves emitted by ultra-light boson clouds around spinning black holes
As a consequence of superradiant instability induced in Kerr black holes,
ultra-light boson clouds can be a source of persistent gravitational waves,
potentially detectable by current and future gravitational-wave detectors.
These signals have been predicted to be nearly monochromatic, with a small
steady frequency increase (spin-up), but given the several assumptions and
simplifications done at theoretical level, it is wise to consider, from the
data analysis point of view, a broader class of gravitational signals in which
the phase (or the frequency) slightly wander in time. Also other types of
sources, e.g. neutron stars in which a torque balance equilibrium exists
between matter accretion and emission of persistent gravitational waves, would
fit in this category. In this paper we present a robust and computationally
cheap analysis pipeline devoted to the search of such kind of signals. We
provide a full characterization of the method, through both a theoretical
sensitivity estimation and through the analysis of syntethic data in which
simulated signals have been injected. The search setup for both all-sky
searches and higher sensitivity directed searches is discussed.Comment: 13 pages, 13 figure
CMB Polarization Data and Galactic Foregrounds: Estimation of Cosmological Parameters
We estimate the accuracy with which various cosmological parameters can be
determined from the CMB temperature and polarization data when various galactic
unpolarized and polarized foregrounds are included and marginalized using the
multi-frequency Wiener filtering technique. We use the specifications of the
future CMB missions MAP and PLANCK for our study. Our results are in
qualitative agreement with earlier results obtained without foregrounds, though
the errors in most parameters are higher because of degradation of the
extraction of polarization signal in the presence of foregrounds.Comment: 6 pages, submitted to MNRA
A method to search for long duration gravitational wave transients from isolated neutron stars using the generalized FrequencyHough
We describe a method to detect gravitational waves lasting
emitted by young, isolated neutron stars, such as those that could form after a
supernova or a binary neutron star merger, using advanced LIGO/Virgo data. The
method is based on a generalization of the FrequencyHough (FH), a pipeline that
performs hierarchical searches for continuous gravitational waves by mapping
points in the time/frequency plane of the detector to lines in the
frequency/spindown plane of the source. We show that signals whose spindowns
are related to their frequencies by a power law can be transformed to
coordinates where the behavior of these signals is always linear, and can
therefore be searched for by the FH. We estimate the sensitivity of our search
across different braking indices, and describe the portion of the parameter
space we could explore in a search using varying fast Fourier Transform (FFT)
lengths.Comment: 15 figure
CMB Lensing Reconstruction on the Full Sky
Gravitational lensing of the microwave background by the intervening dark
matter mainly arises from large-angle fluctuations in the projected
gravitational potential and hence offers a unique opportunity to study the
physics of the dark sector at large scales. Studies with surveys that cover
greater than a percent of the sky will require techniques that incorporate the
curvature of the sky. We lay the groundwork for these studies by deriving the
full sky minimum variance quadratic estimators of the lensing potential from
the CMB temperature and polarization fields. We also present a general
technique for constructing these estimators, with harmonic space convolutions
replaced by real space products, that is appropriate for both the full sky
limit and the flat sky approximation. This also extends previous treatments to
include estimators involving the temperature-polarization cross-correlation and
should be useful for next generation experiments in which most of the
additional information from polarization comes from this channel due to
sensitivity limitations.Comment: Accepted for publication in Phys. Rev. D; typos correcte
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