Spikes in Cosmic Crystallography

Gomero, G. I.; Teixeira, A. F. F.; Rebouçcas, M. J.; Bernui, Armando

doi:10.1142/s0218271802002074

Cited by 34 publications

(71 citation statements)

References 8 publications

(25 reference statements)

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“…Finally, using χ 2 statistics we assess the confidence level of the North/South asymmetry in WMAP data compared to 1000 Monte-Carlo realizations of CMB skies. distances between all pairs of cosmic objects, listed in a catalog, and then constructing the normalized histogram of the number of pairs with a given angular separation versus their angular separation (for details on the pair separation histogram method see, for example, Gomero et al 2002). A catalog with a large number of objects can be divided in a number (say K) of comparable subcatalogs (i.e.…”

Section: Introductionmentioning

confidence: 99%

On the cosmic microwave background large-scale angular correlations

Bernui

Villela

Wuensche

et al. 2006

A&A

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Aims. We study the large-scale angular correlation signatures of the cosmic microwave background (CMB) temperature fluctuations from WMAP data in several spherical cap regions of the celestial sphere, outside the Kp0 or Kp2 cut-sky masks.Methods. We applied a recently proposed method to CMB temperature maps to permit an accurate analysis of their angular correlations in the celestial sphere through the use of normalized histograms of the number of pairs of such objects with a given angular separation versus their angular separation. The method allows for a better comparison of the results from observational data with the expected CMB angular correlations of a statistically isotropic universe, computed from Monte-Carlo maps according to the WMAP best-fit ΛCDM model. Results. We found that the already known, anomalous lack of large-scale power in full-sky CMB maps is mainly due to deficient angular correlations of a quadrupole-like signature. This result is robust with respect to frequency CMB maps and cut-sky masks. Moreover, we also confirm previous results regarding the uneven distribution in the sky of the large-scale power of WMAP data. In a bin-to-bin correlation analyses, measured by the full covariance matrix χ 2 statistic, we found that the angular correlation signatures in opposite Galactic hemispheres are anomalous at a 98%-99% confidence level.

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Section: Introductionmentioning

confidence: 99%

On the cosmic microwave background large-scale angular correlations

Bernui

Villela

Wuensche

et al. 2006

A&A

Self Cite

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“…For a list and discussion of both two-dimensional and three-dimensional methods, see Table 2 of Luminet & Roukema (1999) and the accompanying discussion. The reader should be reminded that while microwave background data is still the most popular for topology analyses, considerable work in three-dimensional methods has been carried out, including, e.g., Lehoucq et al (1996); Roukema (1996); Fagundes & Gausmann (1998b); Roukema & Edge (1997); ; Gomero et al (2002); Lehoucq et al (1999); Fagundes & Gausmann (1998a); Uzan et al (1999); Fagundes & Gausmann (1999); Gomero et al (2000Gomero et al ( , 2001.…”

Section: Introductionmentioning

confidence: 99%

A hint of Poincaré dodecahedral topology in the WMAP first year sky map

Roukema¹,

Lew²,

Cechowska³

et al. 2004

A&A

137

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Abstract. It has recently been suggested by Luminet et al. (2003) that the WMAP data are better matched by a geometry in which the topology is that of a Poincaré dodecahedral model and the curvature is "slightly" spherical, rather than by an (effectively) infinite flat model. A general back-to-back matched circles analysis by Cornish et al. (2004) for angular radii in the range 25−90• , using a correlation statistic for signal detection, failed to support this. In this paper, a matched circles analysis specifically designed to detect dodecahedral patterns of matched circles is performed over angular radii in the range 1−40• on the oneyear WMAP data. Signal detection is attempted via a correlation statistic and an rms difference statistic. Extreme value distributions of these statistics are calculated for one orientation of the 36• "screw motion" (Clifford translation) when matching circles, for the opposite screw motion, and for a zero (unphysical) rotation. The most correlated circles appear for circle radii of α = 11 ± 1• , for the left-handed screw motion, but not for the right-handed one, nor for the zero rotation. The favoured six dodecahedral face centres in galactic coordinates are (l• ) and their opposites. The six pairs of circles independently each favour a circle angular radius of 11 ± 1• . The temperature fluctuations along the matched circles are plotted and are clearly highly correlated. Whether or not these six circle pairs centred on dodecahedral faces match via a 36• rotation only due to unexpected statistical properties of the WMAP ILC map, or whether they match due to global geometry, it is clear that the WMAP ILC map has some unusual statistical properties which mimic a potentially interesting cosmological signal.

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“…While the PSH test is designed to detect topological lensing, it has been pointed out by Gomero et al (2002) that (1) it is likely to miss some part of the real signal of topologically lensed pairs; and (2) it would be insufficient to determine which 3-manifold we live in:…”

Section: The Cosmic Crystallography Methods and Its Variationsmentioning

confidence: 99%

Cosmic crystallography using short-lived objects – Active Galactic Nuclei

Marecki¹,

Roukema²,

Bajtlik

2005

A&A

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Abstract. Cosmic crystallography is based on the principle that peaks in the pair separation histogram (PSH) of objects in a catalogue should be induced by the high number of topologically lensed pairs that are separated by Clifford translations, in excess to "random" pairs of objects. Here we present modifications of this method that successively improve the signal-to-noise ratio by removing a large part of the noise and then false signals induced by selection effects. Given the transient nature of the most readily available tracer objects, Active Galactic Nuclei (AGNs), the former is possible because a natural filter for removing many of the noise pairs is available: when counting pairs of objects in order to create PSHs, only those with nearly identical redshifts need to be counted. This redshift filter (a maximum value of ∆z/z = 0.005) was applied to a compilation of AGN catalogues. Further noise was removed by applying a second filter, a maximum angle ∆θ = 0.075 rad, and a minimum number of pairs n pairs = 3 to find each "bunch of pairs" (BoP) where the vectors (in Euclidean comoving space) defined by pairs are required to be nearly equal, whereas in the PSH only the lengths must be nearly equal. These filters reveal significant signals, which, however, are due to selection effects. A third filter, a minimum length L selec = 150 h −1 Mpc between the (parallel) vectors in a BoP, is found to effectively remove these selection effect pairs. After application of these successive filters, no significant topological signal was found.

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Spikes in Cosmic Crystallography

Cited by 34 publications

References 8 publications

On the cosmic microwave background large-scale angular correlations

On the cosmic microwave background large-scale angular correlations

A hint of Poincaré dodecahedral topology in the WMAP first year sky map

Cosmic crystallography using short-lived objects – Active Galactic Nuclei

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