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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 $Lambda$-CDM model, or from a non-trivial topology.
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We present developing of method of the numerical analysis of polarization in the Gauss--Legendre Sky Pixelization (GLESP) scheme for the CMB maps. This incorporation of the polarization transforms in the pixelization scheme GLESP completes the creation of our new method for the numerical analysis of CMB maps. The comparison of GLESP and HEALPix calculations is done.
A new scheme of sky pixelization is developed for CMB maps. The scheme is based on the Gauss--Legendre polynomials zeros and allows one to create strict orthogonal expansion of the map. A corresponding code has been implemented and comparison with other methods has been done.
Archeops is a balloon-borne experiment designed to measure the temperature fluctuations of the CMB on a large region of the sky ($simeq 30%$) with a high angular resolution (10 arcminutes) and a high sensitivity ($60mu K$ per pixel). Archeops will perform a measurement of the CMB anisotropies power spectrum from large angular scales ($ellsimeq 30$) to small angular scales ($ell simeq 800$). Archeops flew for the first time for a test flight in July 1999 from Sicily to Spain and the first scientific flight took place from Sweden to Russia in January 2001. The data analysis is on its way and I present here preliminary results, realistic simulations showing the expected accuracy on the measurement of the power spectrum and perspectives for the incoming flights (Winter 2001/2003).
A crucial problem for partial sky analysis of CMB polarization is the $E$-$B$ leakage problem. Such leakage arises from the presence of `ambiguous modes that satisfy properties of both $E$ and $B$ modes. Solving this problem is critical for primordial polarization $B$ mode detection in partial sky CMB polarization experiments. In this work we introduce a new method for reducing the leakage. We demonstrate that if we complement the $E$-mode information outside the observation patch with ancillary data from full-sky CMB observations, we can reduce and even effectively remove the $E$-to-$B$ leakage. For this objective, we produce $E$-mode Stokes $QU$ maps from Wiener filtered full-sky intensity and polarization CMB observations. We use these maps to fill the sky region that is not observed by the ground-based experiment of interest, and thus complement the partial sky Stokes $QU$ maps. Since the $E$-mode information is now available on the full sky we see a significant reduction in the $E$-to-$B$ leakage. We evaluate on simulated data sets the performance of our method for a `shallow $f_text{sky}=8%$, and a `deep $f_text{sky}=2%$ northern hemisphere sky patch, with AliCPT-like properties, and a LSPE-like $f_text{sky}=30%$ sky patch, by combining those observations with Planck-like full sky polarization maps. We find that our method outperforms the standard and the pure-$B$ method pseudo-$C_ell$ estimators for all of our simulations. Our new method gives unbiased estimates of the $B$-mode power spectrum through-out the entire multipole range with near-optimal pseudo-$C_ell$ errors for $ell>20$. We also study the application of our method to the CMB-S4 experiment combined with LiteBIRD-like full sky data, and show that using signal-dominated full sky $E$-mode data we can eliminate the $E$-to-$B$ leakage problem.
In a recent preprint (CCC-predicted low-variance circles in the CMB sky and LCDM), Gurzadyan and Penrose (2011) claim for the second time to find evidence for pre-Big Bang activity in the form of concentric circles of low variance in the WMAP data. The same claim was made in November 2010, but quickly shown to be false by three independent groups. The culprit was simply that Gurzadyan and Penroses simulations were based on an inappropriate power spectrum. In the most recent paper, they now claim that the significance is indeed low if the simulations are based on the realization-specific WMAP spectrum (ie., the one directly measured from the sky maps and affected by cosmic variance), but not if the simulations are based on a theoretical LCDM spectrum. In this respect, we note that the three independent reanalyses all based their simulations on the LCDM spectrum, not the observed WMAP spectrum, and this alone should suffice to show that the updated claims are also incorrect. In fact, it is evident from the plots shown in their new paper that the spectrum is still incorrect, although in a different way than in their first paper. Thus, Gurzadyan and Penroses new claims are just as wrong as those made in the first paper, and for the same reason: The simulations are not based on an appropriate power spectrum. Still, while this story is of little physical interest, it may have some important implications in terms of scienctific sociology: Looking back at the background papers leading up to the present series by Gurzadyan and Penrose, in particular one introducing the Kolmogorov statistic, we believe one can find evidence that a community based and open access referee process may be more efficient at rejecting incorrect results and claims than a traditional journal based approach.
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