Ellipsoidal Universe Can Solve the Cosmic Microwave Background Quadrupole Problem

Campanelli, Leonardo; Cea, Paolo; Tedesco, Luigi

doi:10.1103/physrevlett.97.131302

Cited by 163 publications

(110 citation statements)

References 30 publications

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“…This has been mainly motivated by hints of anomalies in the cosmic microwave background (CMB) distribution first observed on the full sky by the WMAP experiment [34][35][36][37]. These were also observed in the Planck experiment [38][39][40][41][42], and followed by many studies, e.g., large angle anomalies [43], with the possible clarifications in the alignment of quadrupole and octupole moments [44][45][46], the large-scale asymmetry [47,48], the strange cold spot [36], and the low quadrupole moment of the CMB [22,42,49]. So far, the local deviations from the statistically highly isotropic Gaussianity of the CMB in some directions (the so-called cold spots) could not have been excluded at high confidence levels [37,38,49,50].…”

Section: Introductionmentioning

confidence: 73%

“…Clearly, there is a considerable discrepancy between the two values. This deficit can be reduced partially by using cosmic variance, viz., ∆T st+variance ≈ 28 µK [22,83]. Here, we look for the possible effects of the expansion anisotropy on the CMB power spectrum.…”

Section: Cmb Quadrupole Problemmentioning

confidence: 99%

“…Depending on the characteristics of the detected expansion anisotropy, it could be illuminating to the nature of inflaton, dark energy (DE) and even gravitation. For instance, altering the stiff-fluid-like behavior of the expansion anisotropy could be possible mainly by either replacing minimally coupled scalar field models of inflaton or DE by a source yielding anisotropic pressure (e.g., vector fields; see [12] for a list of anisotropic stresses and their effects on the expansion anisotropy) or replacing GR by a modified gravity that can give rise to effective source yielding anisotropic pressure (e.g., Brans-Dicke theory [13][14][15]); see, for examples, [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33].…”

Section: Introductionmentioning

confidence: 99%

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Constraints on a Bianchi type I spacetime extension of the standard ΛCDM model

et al. 2019

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We consider the simplest anisotropic generalization, as a correction, to the standard ΛCDM model, by replacing the spatially flat Robertson-Walker metric by the Bianchi type-I metric, which brings in a new term Ωσ0a −6 (mimicking the stiff fluid) in the average expansion rate H(a) of the Universe. From Hubble and Pantheon data, relevant to the late Universe (z 2.4), we obtain the constraint Ωσ0 10 −3 , in line with the model-independent constraints. When the baryonic acoustic oscillations and cosmic microwave background (CMB) data are included, the constraint improves by 12 orders of magnitude, i.e., Ωσ0 10 −15 . We find that this constraint could alter neither the matter-radiation equality redshift nor the peak of the matter perturbations. Demanding that the expansion anisotropy has no significant effect on the standard big bang nucleosynthesis (BBN), we find the constraint Ωσ0 10 −23 . We show explicitly that the constraint from BBN renders the expansion anisotropy irrelevant to make a significant change in the CMB quadrupole temperature, whereas the constraint from the cosmological data in our model provides the temperature change up to ∼ 11 mK, though it is much beyond the CMB quadrupole temperature.

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Section: Introductionmentioning

confidence: 73%

Section: Cmb Quadrupole Problemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Constraints on a Bianchi type I spacetime extension of the standard ΛCDM model

et al. 2019

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“…Campanelli et al [51] describe magnetic fields present at the last scattering epoch resulting in an ellipsoidal universe. Similar effects have been proposed due to moving dark energy [52].…”

Section: Introductionmentioning

confidence: 99%

Anisotropic dark energy: dynamics of the background and perturbations

Koivisto

Mota

2008

J. Cosmol. Astropart. Phys.

179

168

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Abstract. We investigate cosmologies where the accelerated expansion of the Universe is driven by a field with an anisotropic equation of state. We model such scenarios within the Bianchi I framework, introducing two skewness parameters to quantify the deviation of pressure from isotropy. We study the dynamics of the background expansion in these models. A special case of anisotropic cosmological constant is analyzed in detail. The anisotropic expansion is then confronted with the redshift and angular distribution of the supernovae type Ia. In addition, we investigate the effects on the cosmic microwave background (CMB) anisotropies for which the main signature appears to be a quadrupole contribution. We find that the two skewness parameters can be very well constrained. Tightest bounds are imposed by the CMB quadrupole, but there are anisotropic models which avoid this bound completely. Within these bounds, the anisotropy can be beneficial as a potential explanation of various anomalous cosmological observations, especially in the CMB at the largest angles. We also consider the dynamics of linear perturbations in these models. The covariant approach is used to derive the general evolution equations for cosmological perturbations taking into account imperfect sources in an anisotropic background. The implications for the galaxy formation are then studied. These results might help to make contact between the observed anomalies in CMB and large scale structure and fundamental theories exhibiting Lorentz violation.

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“…Thus, our matter sector is composed of two fields: the inflaton, whose perturbations can be introduced exactly as in the FLRW case (see, for example, [34]), and the above anisotropic and massless scalar field φ(η, x). Their perturbations are as follows: 8) where the prime denotes the derivative with respect to η. As we are going to show, the perturbation δφ of the anisotropic scalar field is not dynamically important in the inflationary stage, and can be safely ignored.…”

Section: General Formalismmentioning

confidence: 99%

Cosmological signatures of anisotropic spatial curvature

Pereira

Marugán

Carneiro

2015

J. Cosmol. Astropart. Phys.

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Abstract. If one is willing to give up the cherished hypothesis of spatial isotropy, many interesting cosmological models can be developed beyond the simple anisotropically expanding scenarios. One interesting possibility is presented by shear-free models in which the anisotropy emerges at the level of the curvature of the homogeneous spatial sections, whereas the expansion is dictated by a single scale factor. We show that such models represent viable alternatives to describe the large-scale structure of the inflationary universe, leading to a kinematically equivalent Sachs-Wolfe effect. Through the definition of a complete set of spatial eigenfunctions we compute the two-point correlation function of scalar perturbations in these models. In addition, we show how such scenarios would modify the spectrum of the CMB assuming that the observations take place in a small patch of a universe with anisotropic curvature.

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Ellipsoidal Universe Can Solve the Cosmic Microwave Background Quadrupole Problem

Cited by 163 publications

References 30 publications

Constraints on a Bianchi type I spacetime extension of the standard ΛCDM model

Constraints on a Bianchi type I spacetime extension of the standard ΛCDM model

Anisotropic dark energy: dynamics of the background and perturbations

Cosmological signatures of anisotropic spatial curvature

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