Finsler space–time can explain both parity asymmetry and power deficit seen in CMB temperature anisotropies

Chang, Zhe; Rath, Pranati K.; Sang, Yu; Zhao, Deng; Zhou, Yong

doi:10.1093/mnras/sty1689

Cited by 7 publications

(4 citation statements)

References 43 publications

(58 reference statements)

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“…However, in recent literature there are discussions [1][2][3][4][5][6][7][8]19] and claims of the presence of preferred direction [9-13, 17, 18] in the CMB field or breakdown of rotational invariance of the primordial power spectrum [20][21][22]. These indicate possible hints towards new fundamental physics [23,24,[27][28][29][30]. Apart from the cosmological origin of any possible anisotropic signal in the CMB, a question of equal importance is whether the foreground minimized CMB maps may have any residual systematics, e.g., residual foreground contamination which may potentially induce a breakdown from rotational invariance of the field and consequently give rise to a preferred direction.…”

Section: Introductionmentioning

confidence: 99%

Isotropy statistics of CMB hot and cold spots

Khan

Saha

2022

J. Cosmol. Astropart. Phys.

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Statistical Isotropy of the Cosmic Microwave Background (CMB) radiation has been studied and debated extensively in recent years. Under this assumption, the hot spots and cold spots of the CMB are expected to be uniformly distributed over a 2-sphere. We use the orientation matrix, first proposed by Watson (1965) and Scheidegger (1965) and associated shape and strength parameters (Woodcock, 1977) to analyse whether the hot and cold spots of the observed CMB temperature anisotropy field are uniformly placed. We demonstrate the usefulness of our estimators by using simulated toy models containing non-uniform data. We apply our method on several foreground minimized CMB maps observed by WMAP and Planck over large angular scales. The shape and strength parameters constrain geometric features of possible deviations from uniformity (isotropy) and the power of the anomalous signal. We find that distributions of hot or cold spots in cleaned maps show no unusual signature of clustering or girdling. Instead, we notice a strikingly uniform distribution of hot spots over the full sky. The signal remains robust with respect to the four cleaned maps used and presence or absence of the non-Gaussian cold spot (NGCS). On the partial sky with WMAP KQ75 and Planck U73 masks we find anomalously low strength of non-uniformity for cold spots which is found to be robust with respect to various cleaning methods, masks applied, instruments, frequencies, and the presence or absence of the NGCS. Interestingly we find that the signal of anomalously weak non-uniformity could be due to contributions from the quadrupole and octupole and may be related with the low CMB temperature variance anomaly.

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Section: Introductionmentioning

confidence: 99%

Isotropy statistics of CMB hot and cold spots

Khan

Saha

2022

J. Cosmol. Astropart. Phys.

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show abstract

“…Under the assumption of rotational invariance of the primordial curvature perturbation power spectrum, which contains snapshots of quantum scalar field fluctuations on different scales at the time of horizon crossing during inflation, the observable CMB is expected to be statistically isotropic without picking up any preferred direction in the radiation field. However, in recent literature there are discussions [1,2,3,4,5,6,7,8,16] and claims of the presence of preferred direction [9,10,11,12,13,14,15] in the CMB field and (or) breakdown of rotational invariance of the primordial power spectrum [17,18,19] indicating possible hints towards new fundamental physics [20,21,22,23,24,25]. Apart from the cosmological origin of any possible anisotropic signal in the CMB, a question of equal importance is whether the foreground minimized CMB maps may have any residual systematics, e.g., residual foreground contamination which may potentially induce a breakdown from rotational invariance of the field and consequently give rise to a preferred direction.…”

Section: Introductionmentioning

confidence: 99%

Isotropy statistics of CMB hot and cold spots

Khan,

Saha

2021

Preprint

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Statistical Isotropy of the Cosmic Microwave Background (CMB) radiation has been studied and debated extensively in recent years. Under this assumption, the hot spots and cold spots of the CMB are expected to be uniformly distributed over a 2-sphere. We use the orientation matrix and associated shape and strength parameters, first proposed by Watson, to analyse whether the placements of hot and cold spots of the CMB temperature anisotropy field are uniformly distributed. We demonstrate the usefulness of our estimators by using simulated toy models containing non-uniform data. We apply our method on several foreground minimised CMB maps observed by WMAP and Planck over large angular scales. The shape and strength parameters constrain geometric features of possible deviations from uniformity (isotropy) and the power of the anomalous signal. We find that distributions of hot or cold spots in cleaned maps show no unusual signature of clustering or girdling. Instead, we notice a strikingly uniform distribution of hot spots over the full sky. The signal remains robust with respect to the four cleaned maps used and presence or absence of the non-Gaussian cold spot (NGCS). On the partial sky with WMAP KQ75 and Planck U73 masks we find unusual uniformity for cold spots which is found to be robust with respect to various cleaning methods, masks applied, instruments, frequencies, and the presence or absence of the NGCS.

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“…Besides, modifications to the scale of the primordial power ( [26], [8], [23]) may serve as a starting point for explaining the 'parity asymmetry' and other power deficit anomalies. An excellent propo-sition of a Finsler spacetime [9] also helps naturally explain parity asymmetry.…”

Section: Introductionmentioning

confidence: 99%

Anomalous spacings of the CMB temperature angular power spectrum

Khan¹,

Saha²

2021

Preprint

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In this article, we propose a novel technique to test for anomalous features in the CMB. We analyse separations of the observed CMB angular power spectrum (C ) using temperature anisotropy data from WMAP 9 year ILC and 2018 Planck maps of Commander, NILC and SMICA. We estimate the minimum, maximum, average separations and ratios of the maximum to minimum separations between consecutive multipoles of the weighted spectrum, f ( )C . We see that such f ( )'s with higher multipole powers mitigate the parity asymmetry anomaly. For anomalous separations, we find that data exhibits anomalous ranges of multipoles defined by different max and min values, specifically for the entire range of multipoles from 2 − 31 of this work. Without parity based distinctions, most significantly, the maximum separation of the range 8 ≤ ≤ 31 is seen to be anomalously low at the 99.93% confidence level for f ( ) = (WMAP), ( +1) 2π (Planck NILC), the latter indicating a strong deviation from the Sachs-Wolfe plateau for maximum separations among low multipoles. The analysis is repeated for odd and even multipoles taken separately, in the same multipole ranges. Most noticeably, the even multipoles are seen to have anomalously low maximum and average separations relative to their odd counterparts, the most outstanding among which is the anomalously low maximum separation for even multipoles in the range 6 ≤ ≤ 31 for f ( ) = (WMAP), at the 99.77% confidence level. For separation ratios, the multipole ranges are similar to those which turn up as anomalous when only separations are considered.

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Finsler space–time can explain both parity asymmetry and power deficit seen in CMB temperature anisotropies

Cited by 7 publications

References 43 publications

Isotropy statistics of CMB hot and cold spots

Isotropy statistics of CMB hot and cold spots

Isotropy statistics of CMB hot and cold spots

Anomalous spacings of the CMB temperature angular power spectrum

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