arXiv subjects

Nicola Vittorio

Publications and source records attributed to Nicola Vittorio.

40 records · Page 3Linked to original sources

arXiv1997

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 ($\sim 5'$) simulations of the CMB anisotropy pattern. We also discuss the inverse problem, that of evaluating from such a map the full set of $a_{\ell m}$'s and the spectral coefficients $C_\ell$. 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.

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arXiv1996

Polarization of the Microwave Background: theoretical framework

We present a brief review of the polarization properties of the cosmic microwave background in dark matter models for structure formation. Quite independently of the model parameters, the polarization level is expected to be $\sim 10%$ of the anisotropy signal at angular scales $\le 1^o$. Detections of polarization at larger angular scales would provide a strong evidence in favour of an early reionization of the intergalactic medium.

astro-ph↗

arXiv1996

CMB anisotropy at degree angular scales and the thermal history of the Universe

We study the anisotropy of the cosmic microwave background (CMB) in cold and mixed dark matter (CDM and MDM) models, with non scale-invariant primordial power spectra (i.e. $n \neq 1$) and a late, sudden reionization of the intergalactic medium at redshift $z_{rh}$. We test these models against recent detections of CMB anisotropy at large and intermediate angular scales. We find that current CMB anisotropy measurements cannot discriminate between CDM and MDM models. Our likelihood analysis indicates that models with blue power spectra ($n \simeq 1.2$) and a reionization at $z_{rh} \sim 20$ are most consistent with the anisotropy data considered here. Without reionization our analysis gives $1.0 \le n \le 1.26$ (95 % C.L.) for $Ω_b = 0.05$.

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arXiv1993

Reionization and Cosmic Microwave Anisotropies

The effects of reionization, occurring after standard recombination in cold dark matter-dominated models, on CMB anisotropies are investigated. Late-time reionization reduces the CMB anisotropies, in particular, on degree scales. It is found that constraints on cold dark matter-dominated models from the highest frequency channel of the 9-point South Pole data are significantly relaxed for models which are consistent with Big Bang nucleosynthesis if reionization is assumed to have occurred by redshift $\sim 20.$

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