R. Fabbri

The Effect of Primordially Produced Gravitons upon the Anisotropy of the Cosmological Microwave Background Radiation

Abstract We consider the effect of primordially produced gravitons on the anisotropy of the cosmological microwave background radiation. For a universe that includes a phase of exponential expansion, we derive an upper limit upon the associated vacuum energy density. This limit coincides with the one found by Rubakov et al., but our calculations differ from theirs in several important respects. Recent supersymmetric inflationary model universes are compatible with this limit, but models in which the exponential expansion is caused by trace-anomaly effects appear to be ruled out. We finally provide a detailed analysis of the harmonic content of the background anisotropy and show the relevance of harmonics with relatively large l .

The angular power spectra of polarized Galactic synchrotron

Abstract We derive the angular power spectra of intensity and polarization of Galactic synchrotron emission in the range 36≤l≲103 from the Parkes survey mapping the southern Galactic plane at 2.4 GHz. The polarization spectra of both electric and magnetic parity up to l≃103 are approximated very well by power laws with slope coefficients ≃1.4, quite different from the CMB spectra. We show that no problem should arise from Galactic synchrotron for measurements of CMB polarization in the cosmological window.

Polarization Angular Spectra of Galactic Synchrotron Emission on Arcminute Scales

We study the angular power spectra of the polarized component of the Galactic synchrotron emission in the 28 deg2 test region of the Southern Galactic Plane Survey at 1.4 GHz. These data were obtained by the Australia Telescope Compact Array and allow us to investigate angular power spectra down to arcminute scales. We find that, at this frequency, the polarization spectra for E- and B-modes seem to be affected by Faraday rotation produced in compact foreground screens. A different behavior is shown by the angular spectrum of the polarized intensity PI = (Q2 + U2)1/2. This is well fitted by a power law (CPIl ∝ l−αPI) with slope ~1.7, which agrees with higher frequency results and can probably be more confidently extrapolated to the cosmological window.

The Sky Polarization Observatory

Abstract The Sky Polarization Observatory (SPOrt) is an ASI-funded experiment specifically designed to measure the sky polarization at 22, 32 and 90 GHz, which was selected in 1997 by ESA to be flown on the International Space Station. Starting in 2006 and for at least 18 months, it will be taking direct and simultaneous measurements of the Stokes parameters Q and U at 660 sky pixels, with FWHM=7°. Due to development efforts over the past few years, the design specifications have been significantly improved with respect to the first proposal. Here we present an up-to-date description of the instrument, which now warrants a pixel sensitivity of 1.7 μK for the polarization of the cosmic background radiation, assuming two years of observations. We discuss SPOrt scientific goals in the light of WMAP results, in particular in connection with the emerging double-reionization cosmological scenario.

The power-law behaviours of angular spectra of polarized Galactic synchrotron

Abstract We study the angular power spectra of polarized Galactic synchrotron in the range 10≲l≤800, at several frequencies between 0.4 and 2.7 GHz and at several Galactic latitudes up to near the North Galactic Pole. Electric- and magnetic-parity polarization spectra are found to have slopes around αE,B=1.4–1.5 in the Parkes and Effelsberg Galactic-Plane surveys, but strong local fluctuations of αE,B are found at |b|≃10° from the 1.4 GHz Effelsberg survey. The CPIl spectrum, which is insensitive to the polarization direction, is somewhat steeper, being αPI=1.6–1.8 for the same surveys. The low-resolution multifrequency survey of Brouw and Spoelstra [A&AS 26 (1976) 129] shows some flattening of the spectra below 1 GHz, more intense for CE,Bl than for CPIl. In no case we find evidence for really steep spectra. The extrapolation to the cosmological window shows that at 90 GHz the detection of E-mode harmonics in the cosmic background radiation should not be disturbed by synchrotron, even around l≃10 for a reionization optical depth τri≳0.05.

Cosmic microwave background anisotropies resulting from feedback-regulated inhomogeneous reionization

We calculate the secondary anisotropies in the CMB produced by inhomogeneous reionization from simulations in which the effects of radiative and stellar feedback effects on galaxy formation have been included. This allows to self-consistently determine the beginning (

A polarized synchrotron template for cosmic microwave background polarization experiments based on WMAP data

z_i\approx 30

Multipole anisotropies of the cosmic background radiation and inflationary models

), the duration (

Large-scale anisotropies of the cosmic background radiation in generalized inflationary cosmologies

\delta z\approx 20

A new approach for a Galactic synchrotron polarized emission template in the microwave range

) and the (nonlinear) evolution of the reionization process for a critical density CDM model. In addition, from the simulated spatial distribution of ionized regions, we are able to calculate the evolution of the two-point ionization correlation function,