Unveiling hidden patterns in CMB anisotropy maps

Ghosh, T.; Hajian, Amir; Souradeep, T.

doi:10.1103/physrevd.75.083007

Cited by 52 publications

(74 citation statements)

References 49 publications

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“…A number of authors have attempted to explain the observed quadrupole-octopole correlations in terms of a new foreground [51][52][53][54][55][56]. (Some of these also attempted to explain the absence of large angle correlations, for which there are also other proffered explanations [57][58][59][60][61][62][63].)…”

Section: Discussionmentioning

confidence: 99%

Uncorrelated universe: Statistical anisotropy and the vanishing angular correlation function in WMAP years 1–3

et al. 2007

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The large-angle (low-ℓ) correlations of the Cosmic Microwave Background (CMB) as reported by the Wilkinson Microwave Anisotropy Probe (WMAP) after their first year of observations exhibited statistically significant anomalies compared to the predictions of the standard inflationary big-bang model. We suggested then that these implied the presence of a solar system foreground, a systematic correlated with solar system geometry, or both. We re-examine these anomalies for the data from the first three years of WMAP's operation. We show that, despite the identification by the WMAP team of a systematic correlated with the equinoxes and the ecliptic, the anomalies in the firstyear Internal Linear Combination (ILC) map persist in the three-year ILC map, in all-but-one case at similar statistical significance. The three-year ILC quadrupole and octopole therefore remain inconsistent with statistical isotropy -they are correlated with each other (99.6%C.L.), and there are statistically significant correlations with local geometry, especially that of the solar system. The angular two-point correlation function at scales > 60 degrees in the regions outside the (kp0) galactic cut, where it is most reliably determined, is approximately zero in all wavebands and is even more discrepant with the best fit ΛCDM inflationary model than in the first-year data -99.97%C.L. for the new ILC map. The full-sky ILC map, on the other hand, has a non-vanishing angular two-point correlation function, apparently driven by the region inside the cut, but which does not agree better with ΛCDM. The role of the newly identified low-ℓ systematics is more puzzling than reassuring.

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Section: Discussionmentioning

confidence: 99%

Uncorrelated universe: Statistical anisotropy and the vanishing angular correlation function in WMAP years 1–3

et al. 2007

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“…(20). It is obvious that the contributions of these time dependent terms to the energy cannot compensate the infinite value of (P 0 ) 2 corresponding to the constant mode, which implies that the total contribution to (P 0 ) 2 due to the j = 2 k-interval cannot become finite.…”

Section: A Scalar Perturbationsmentioning

confidence: 99%

Probing the creatable character of perturbed Friedmann-Robertson-Walker universes

Lapiedra

Sáez

2008

Phys. Rev. D

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We discuss whether some perturbed Friedmann-Robertson-Walker (FRW) universes could be creatable, i. e., could have vanishing energy, linear momentum and angular momentum, as it could be expectable if the Universe arose as a quantum fluctuation. On account of previous results, the background is assumed to be either closed (with very small curvature) or flat. In the first case, fully arbitrary linear perturbations are considered; whereas in the flat case, it is assumed the existence of: (i) inflationary scalar perturbations, that is to say, Gaussian adiabatic scalar perturbations having an spectrum close to the Harrison-Zel'dovich one, and (ii) arbitrary tensor perturbations.We conclude that, any closed perturbed universe is creatable, and also that, irrespective of the spectrum and properties of the inflationary gravitational waves, perturbed flat FRW universes with standard inflation are not creatable. Some considerations on pre-inflationary scalar perturbations are also presented. The creatable character of perturbed FRW universes is studied, for the first time, in this paper.

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“…A modified template fitting technique was performed by Land & Magueijo (2006) and, although a statistically significant template fit was not reported, the corresponding "corrected" WMAP data were again free of many large scale "anomalies". Subsequently, Ghosh et al (2007) used the bipolar power spectrum of WMAP data to constrain the amplitude of any Bianchi component in the CMB. Due to the renewed interest in Bianchi models, solutions to the CMB temperature fluctuations induced in Bianchi VII h models when incorporating dark energy were since derived by Jaffe et al (2006c) and Bridges et al (2007).…”

Section: Previous Resultsmentioning

confidence: 99%

Planck2013 results. XXVI. Background geometry and topology of the Universe

Ade¹,

Aghanim²,

Arnaud³

et al. 2014

A&A

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The new cosmic microwave background (CMB) temperature maps from Planck provide the highest-quality full-sky view of the surface of last scattering available to date. This allows us to detect possible departures from the standard model of a globally homogeneous and isotropic cosmology on the largest scales. We search for correlations induced by a possible non-trivial topology with a fundamental domain intersecting, or nearly intersecting, the last scattering surface (at comoving distance χ rec ), both via a direct search for matched circular patterns at the intersections and by an optimal likelihood search for specific topologies. For the latter we consider flat spaces with cubic toroidal (T3), equal-sided chimney (T2) and slab (T1) topologies, three multi-connected spaces of constant positive curvature (dodecahedral, truncated cube and octahedral) and two compact negative-curvature spaces. These searches yield no detection of the compact topology with the scale below the diameter of the last scattering surface. For most compact topologies studied the likelihood maximized over the orientation of the space relative to the observed map shows some preference for multi-connected models just larger than the diameter of the last scattering surface. Since this effect is also present in simulated realizations of isotropic maps, we interpret it as the inevitable alignment of mild anisotropic correlations with chance features in a single sky realization; such a feature can also be present, in milder form, when the likelihood is marginalized over orientations. Thus marginalized, the limits on the radius R i of the largest sphere inscribed in topological domain (at log-likelihood-ratio ∆ln L > −5 relative to a simply-connected flat Planck best-fit model) are: in a flat Universe, R i > 0.92χ rec for the T3 cubic torus; R i > 0.71χ rec for the T2 chimney; R i > 0.50χ rec for the T1 slab; and in a positively curved Universe, R i > 1.03χ rec for the dodecahedral space; R i > 1.0χ rec for the truncated cube; and R i > 0.89χ rec for the octahedral space. The limit for a wider class of topologies, i.e., those predicting matching pairs of back-to-back circles, among them tori and the three spherical cases listed above, coming from the matched-circles search, is R i > 0.94χ rec at 99% confidence level. Similar limits apply to a wide, although not exhaustive, range of topologies. We also perform a Bayesian search for an anisotropic global Bianchi VII h geometry. In the non-physical setting where the Bianchi cosmology is decoupled from the standard cosmology, Planck data favour the inclusion of a Bianchi component with a Bayes factor of at least 1.5 units of log-evidence. Indeed, the Bianchi pattern is quite efficient at accounting for some of the large-scale anomalies found in Planck data. However, the cosmological parameters that generate this pattern are in strong disagreement with those found from CMB anisotropy data alone. In the physically motivated setting where the Bianchi parameters are coupled and fitted simultaneousl...

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Unveiling hidden patterns in CMB anisotropy maps

Cited by 52 publications

References 49 publications

Uncorrelated universe: Statistical anisotropy and the vanishing angular correlation function in WMAP years 1–3

Uncorrelated universe: Statistical anisotropy and the vanishing angular correlation function in WMAP years 1–3

Probing the creatable character of perturbed Friedmann-Robertson-Walker universes

Planck2013 results. XXVI. Background geometry and topology of the Universe

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