Statistical isotropy of CMB polarization maps

Basak, S.; Hajian, Amir; Souradeep, T.

doi:10.1103/physrevd.74.021301

Cited by 44 publications

(43 citation statements)

References 12 publications

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“…On the other hand, largescale CMB polarization measurements are still in their infancy and provide fertile grounds for future tests of * Hubble Fellow † Electronic address: cdvorkin@uchicago.edu isotropy. While generic tests of isotropy have also been proposed for polarization [24,25] and unrelated statistical anomalies may be found, any physical model that purports to explain the temperature anomalies provides testable predictions for the statistics of the polarization field. Matching anomalies in polarization for such models can provide a means of going beyond both a posteriori inferences and blind searches for isotropy anomalies.…”

Section: Introductionmentioning

confidence: 99%

Testable polarization predictions for models of CMB isotropy anomalies

2008

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Anomalies in the large-scale CMB temperature sky measured by WMAP have been suggested as possible evidence for a violation of statistical isotropy on large scales. In any physical model for broken isotropy, there are testable consequences for the CMB polarization field. We develop simulation tools for predicting the polarization field in models that break statistical isotropy locally through a modulation field. We study two different models: dipolar modulation, invoked to explain the asymmetry in power between northern and southern ecliptic hemispheres, and quadrupolar modulation, posited to explain the alignments between the quadrupole and octopole. For the dipolar case, we show that predictions for the correlation between the first 10 multipoles of the temperature and polarization fields can typically be tested at better than the 98% CL. For the quadrupolar case, we show that the polarization quadrupole and octopole should be moderately aligned. Such an alignment is a generic prediction of explanations which involve the temperature field at recombination and thus discriminate against explanations involving foregrounds or local secondary anisotropy. Predicted correlations between temperature and polarization multipoles out to ℓ = 5 provide tests at the ∼ 99% CL or stronger for quadrupolar models that make the temperature alignment more than a few percent likely. As predictions of anomaly models, polarization statistics move beyond the a posteriori inferences that currently dominate the field.

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Section: Introductionmentioning

confidence: 99%

Testable polarization predictions for models of CMB isotropy anomalies

2008

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“…The bipolar power spectrum is a measure of statistical isotropy in CMB anisotropy maps and is zero when statistical isotropy obtains. Properties of BiPS have been studied in great detail in [22,23]. We show that, although correcting the WMAP first-year maps for the Bianchi template may explain some features in the WMAP data [24], this is done at the expense of introducing some anomalies such as preferred directions and the violation of statistical isotropy into the Bianchi corrected maps.…”

Section: Introductionmentioning

confidence: 99%

Unveiling hidden patterns in CMB anisotropy maps

2007

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Bianchi VII h models have been recently proposed to explain potential anomalies in the CMB anisotropy as observed by WMAP. We investigate the violation of statistical isotropy due to an embedded Bianchi VII h template in the CMB anisotropy maps to determine whether the existence of a hidden Bianchi template in the WMAP data is consistent with the previous null detection of the bipolar power spectrum in the WMAP first-year maps. We argue that, although correcting the WMAP maps for the Bianchi template may explain some features in the WMAP data, it may cause other anomalies such as preferred directions leading to detectable levels of violation of statistical isotropy in the Bianchi corrected maps. We compute the bipolar power spectrum for the low density Bianchi VII h models embedded in the background CMB anisotropy maps with the power spectrum that have been shown in recent literature to best fit the first-year WMAP data. By examining the statistical isotropy of these maps, we put a limit of H 0 2:77 10 ÿ10 99% C:L: on the shear parameter in Bianchi VII h models.

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“…(3), thereby making C l an inadequate quantity to characterize the statistical properties of the temperature field [18]. Under such a situation, bipolar spherical harmonic expansion, proposed by Hajian and Souradeep [19][20][21][22][23][24], proves to be the most general representation of the two-point correlation function, where the angular power spectrum C l is a subset of bipolar spherical harmonic coefficients (BipoSH). The two-point correlation function of CMB anisotropies can be expanded as…”

Section: Bipolar Formalism and The Observable Measuresmentioning

confidence: 99%

“…Since the bipolar formalism is sensitive to structures and patterns in the underlying two-point correlation function, particularly the real space correlations, it is a novel tool to characterize statistical anisotropies [19][20][21][22][23][24]. Rotational symmetry about a preferred axis (sayẑ) is the simplest way to break SI.…”

Section: Bipolar Representation Of Cmb Correlation Symmetriesmentioning

confidence: 99%

Bipolar harmonic encoding of CMB correlation patterns

et al. 2010

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Deviations from statistical isotropy can be modeled in various ways, for instance, anisotropic cosmological models (Bianchi models), compact topologies, and presence of primordial magnetic field. Signature of anisotropy manifests itself in cosmic microwave background correlation patterns. Here we explore the symmetries of the correlation function and its implications on the observable measures constructed within the bipolar harmonic formalism for these variety of models. Different quantifiers within the bipolar harmonic representation are used to distinguish between plausible models of breakdown of statistical isotropy and as a spectroscopic tool for discriminating between distinct cosmic topology.

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Statistical isotropy of CMB polarization maps

Cited by 44 publications

References 12 publications

Testable polarization predictions for models of CMB isotropy anomalies

Testable polarization predictions for models of CMB isotropy anomalies

Unveiling hidden patterns in CMB anisotropy maps

Bipolar harmonic encoding of CMB correlation patterns

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