Signals of statistical anisotropy in<i>WMAP</i>foreground-cleaned maps

Samal, Pramoda Kumar; Saha, Rajib; Jain, Pankaj; Ralston, John P.

doi:10.1111/j.1365-2966.2009.14728.x

Cited by 41 publications

(38 citation statements)

References 89 publications

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“…The Power tensor is a robust diagnostic to test isotropy of CMB data (Ralston & Jain 2004;Samal et al 2008Samal et al , 2009. The CMB temperature is conventionally expanded in terms of spherical harmonics Y lm (n):…”

Section: Power Tensor Power Entropy and Alignment Statisticsmentioning

confidence: 99%

Alignments of parity even/odd-only multipoles in CMB

Aluri

Ralston

Weltman

2017

Monthly Notices of the Royal Astronomical Society

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We compare the statistics of parity even and odd multipoles of the cosmic microwave background (CMB) sky from PLANCK full mission temperature measurements. An excess power in odd multipoles compared to even multipoles has previously been found on large angular scales. Motivated by this apparent parity asymmetry, we evaluate directional statistics associated with even compared to odd multipoles, along with their significances. Primary tools are the Power Tensor and Alignment Tensor statistics. We limit our analysis to the first sixty multipoles i.e., l = [2, 61]. We find no evidence for statistically unusual alignments of even parity multipoles. More than one independent statistic finds evidence for alignments of anisotropy axes of odd multipoles, with a significance equivalent to ∼ 2σ or more. The robustness of alignment axes is tested by making galactic cuts and varying the multipole range. Very interestingly, the region spanned by the (a)symmetry axes is found to broadly contain other parity (a)symmetry axes previously observed in the literature.

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Section: Power Tensor Power Entropy and Alignment Statisticsmentioning

confidence: 99%

Alignments of parity even/odd-only multipoles in CMB

Aluri

Ralston

Weltman

2017

Monthly Notices of the Royal Astronomical Society

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“…Among these anomalies, there is a strong alignment between the preferred axes of the quadrupole and the octopole, which is commonly referred to as the axis of evil [3,1,11,16,15]. The claims of the existence of a preferred direction in the CMB temperature map have led to a discussion about whether this is simply due to a chance fluctuation in the CMB temperature map, if it can be blamed on local structures or on systematics in the measurement, or whether it is actually due to a preferred direction intrinsic to the geometry of the primordial Universe [4,12,17,8,13,18,10].…”

Section: Introductionmentioning

confidence: 99%

The Axis of Evil - A Polarization Perspective

Frommert¹,

Enßlin²

2010

Proceedings of International Workshop on Cosmic Structure and Evolution — PoS(Cosmology2009)

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We search for an unusual alignment of the preferred axes of the quadrupole and octopole, the so-called axis of evil, in the WMAP polarization data. We split the polarization map into a part correlated with the temperature and an uncorrelated part. We then determine the preferred axes for the quadrupole and octopole in the uncorrelated polarization map, which serves as a statistically independent probe of the axis of evil. We find that the axis of the quadrupole aligns with the axis of evil within our measurement precision, whereas the axis of the octopole does not. However, with our measurement uncertainty, the probability of at least one axis aligning by chance in an isotropic universe is of the order of 50 per cent. Nevertheless, our analysis of the axis of evil promises to be a powerful tool when applied to data expected from the Planck satellite. Structure and Evolution -Cosmology2009, International Workshop on Cosmic

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“…A very low value of S X compared to log(3) indicates a violation of isotropy. Here we mainly focus on the low-l anomaly such as alignment between CMB quadrupole and octopole in PLANCK data in comparison to WMAP 9-year data and also the high-l anomaly seen in [7] using the foreground cleaned maps provided by WMAP team.…”

Section: Introductionmentioning

confidence: 99%

“…Here, we used the power tensor technique [4,6,7] to study the the low-l anomaly such as alignment between CMB quadrupole and octopole in PLANCK data in comparison to WMAP 9-year data. Here, we revisit the statistics defined earlier in [6,7] to study the low-l alignment as well as the high-l anomaly seen in [7] for WMAP-9 year foreground cleaned data.…”

Section: Introductionmentioning

confidence: 99%

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Testing isotropy of cosmos with WMAP and PLANCK data

Rath

Samal

2015

Mod. Phys. Lett. A

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In recent years, there have been a large number of studies which support violation of statistical isotropy. Meanwhile there are some studies which also found inconsistency. We use the power tensor method defined earlier in the literature to study the new CMBR data. The orientation of these three orthogonal vectors, as well as the power associated with each vector, contains information about possible violation of statistical isotropy. This information is encoded in two entropy measures, the power-entropy and alignment-entropy. We apply this method to WMAP 9-year and PLANCK data. Here, we also revisit the statistics to test high-l anomaly reported in our earlier paper and find that the high degree of isotropy seen in earlier WMAP 5-year data is absent in the revised WMAP-9 year data.

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Signals of statistical anisotropy inWMAPforeground-cleaned maps

Cited by 41 publications

References 89 publications

Alignments of parity even/odd-only multipoles in CMB

Alignments of parity even/odd-only multipoles in CMB

The Axis of Evil - A Polarization Perspective

Testing isotropy of cosmos with WMAP and PLANCK data

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