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Anomalies and Tensions of the Cosmic Microwave Background

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A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Physics".

Deadline for manuscript submissions: closed (31 December 2019) | Viewed by 15185

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Dr. Eleonora Di Valentino

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Guest Editor

School of Mathematics and Statistics, University of Sheffield, Sheffield S3 7RH, UK
Interests: cosmology; CMB; dark energy; modified gravity; neutrinos
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Dear Colleagues,

With the recent release of the Cosmic Microwave Background (CMB) anisotropies of the Planck satellite, we entered in the era of the ‘Tension Cosmology’. Despite the fact that these measurments provided a strong confirmation of the LambdaCDM model, a few interesting tensions and anomalies are emerging. We can identify some internal inconsistencies present in the Planck data, and some external tensions with non-CMB datasets. All these anomalies can be due to systematics in the cosmological experiments, or more interesting, can be due to physics beyond the standard model.

Dr. Eleonora Di Valentino
Guest Editor

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Keywords

Cosmic Microwave Background
Extensions of LCDM
Dark energy
Modified Gravity

Published Papers (4 papers)

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Research

24 pages, 1651 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Revisiting a Negative Cosmological Constant from Low-Redshift Data

by Luca Visinelli, Sunny Vagnozzi and Ulf Danielsson

Symmetry 2019, 11(8), 1035; https://doi.org/10.3390/sym11081035 - 10 Aug 2019

Cited by 117 | Viewed by 4579

Abstract

Persisting tensions between high-redshift and low-redshift cosmological observations suggest the dark energy sector of the Universe might be more complex than the positive cosmological constant of the

Λ

CDM model. Motivated by string theory, wherein symmetry considerations make consistent AdS backgrounds (i.e., maximally-symmetric [...] Read more.

Λ

CDM model. Motivated by string theory, wherein symmetry considerations make consistent AdS backgrounds (i.e., maximally-symmetric spacetimes with a negative cosmological constant) ubiquitous, we explore a scenario where the dark energy sector consists of two components: a negative cosmological constant, with a dark energy component with equation of state

w_{ϕ}

on top. We test the consistency of the model against low-redshift baryon acoustic oscillation and Type Ia supernovae distance measurements, assessing two alternative choices of distance anchors: the sound horizon at baryon drag determined by the Planck collaboration and the Hubble constant determined by the SH0ES program. We find no evidence for a negative cosmological constant and mild indications for an effective phantom dark energy component on top. A model comparison analysis reveals that the

Λ

CDM model is favoured over our negative cosmological constant model. While our results are inconclusive, should low-redshift tensions persist with future data, it would be worth reconsidering and further refining our toy negative cosmological constant model by considering realistic string constructions. Full article

(This article belongs to the Special Issue Anomalies and Tensions of the Cosmic Microwave Background)

23 pages, 1789 KiB

Open AccessEditor’s ChoiceArticle

CMB Tensions with Low-Redshift H₀ and S₈ Measurements: Impact of a Redshift-Dependent Type-Ia Supernovae Intrinsic Luminosity

by Matteo Martinelli and Isaac Tutusaus

Symmetry 2019, 11(8), 986; https://doi.org/10.3390/sym11080986 - 02 Aug 2019

Cited by 51 | Viewed by 3871

Abstract

With the recent increase in precision of our cosmological datasets, measurements of

Λ

CDM model parameter provided by high- and low-redshift observations started to be in tension, i.e., the obtained values of such parameters were shown to be significantly different in a statistical [...] Read more.

With the recent increase in precision of our cosmological datasets, measurements of

Λ

H_{0}

, and the weighted amplitude of matter fluctuations,

S_{8}

, obtained from local or low-redshift measurements and from cosmic microwave background (CMB) observations. We combine the main approaches previously used in the literature by extending the cosmological model and accounting for extra systematic uncertainties. With such analysis we aim at exploring non standard cosmological models, implying deviation from a cosmological constant driven acceleration of the Universe expansion, in the presence of additional uncertainties in measurements. In more detail, we reconstruct the Dark Energy equation of state as a function of redshift, while we study the impact of type-Ia supernovae (SNIa) redshift-dependent astrophysical systematic effects on these tensions. We consider a SNIa intrinsic luminosity dependence on redshift due to the star formation rate in its environment, or the metallicity of the progenitor. We find that the

H_{0}

and

S_{8}

tensions can be significantly alleviated, or even removed, if we account for varying Dark Energy for SNIa and CMB data. However, the tensions remain when we add baryon acoustic oscillations (BAO) data into the analysis, even after the addition of extra SNIa systematic uncertainties. This points towards the need of either new physics beyond late-time Dark Energy, or other unaccounted systematic effects (particulary in BAO measurements), to fully solve the present tensions. Full article

(This article belongs to the Special Issue Anomalies and Tensions of the Cosmic Microwave Background)

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22 pages, 1226 KiB

Open AccessArticle

Testing Predictions of the Quantum Landscape Multiverse 3: The Hilltop Inflationary Potential

by Eleonora Di Valentino and Laura Mersini-Houghton

Symmetry 2019, 11(4), 520; https://doi.org/10.3390/sym11040520 - 10 Apr 2019

Cited by 7 | Viewed by 2282

Abstract

Here we test the predictions of the theory of the origin of the universe from the landscape multiverse, against the 2015 Planck data, for the case of the Hilltop class of inflationary models, for

p = 4

and

p = 6

. By [...] Read more.

Here we test the predictions of the theory of the origin of the universe from the landscape multiverse, against the 2015 Planck data, for the case of the Hilltop class of inflationary models, for

p = 4

and

p = 6

. By considering the quantum entanglement correction of the multiverse, we can place just a lower limit on the local ’SUSY-breaking’ scale, respectively

b > 8.7 \times 10^{6} G e V

95 %

c.l. and

b > 1.3 \times 10^{8} G e V

95 %

c.l. from Planck TT+lowP, so the case with multiverse correction is statistically indistinguishable from the case with an unmodified inflation. We find that the series of anomalies predicted by the quantum landscape multiverse for the allowed range of b, is consistent with Planck’s tests of the anomalies. In addition, the friction between the two cosmological probes of the Hubble parameter and with the weak lensing experiments goes away for a particular subset, the

p = 6

case of Hilltop models. Full article

(This article belongs to the Special Issue Anomalies and Tensions of the Cosmic Microwave Background)

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10 pages, 552 KiB

Open AccessArticle

Exploring the Tension between Current Cosmic Microwave Background and Cosmic Shear Data

by Eleonora Di Valentino and Sarah Bridle

Symmetry 2018, 10(11), 585; https://doi.org/10.3390/sym10110585 - 02 Nov 2018

Cited by 45 | Viewed by 3684

Abstract

This paper provides a snapshot of the formal

S_{8} \equiv σ_{8} \sqrt{Ω_{m} / 0.3}

tension between Planck 2015 and the Kilo Degree Survey of450 deg

^{2}

of imaging data (KiDS-450) or the Canada France Hawaii Lensing Survey (CFHTLenS). We find [...] Read more.

This paper provides a snapshot of the formal

S_{8} \equiv σ_{8} \sqrt{Ω_{m} / 0.3}

tension between Planck 2015 and the Kilo Degree Survey of450 deg

^{2}

of imaging data (KiDS-450) or the Canada France Hawaii Lensing Survey (CFHTLenS). We find that the Cosmic Microwave Bckground (CMB) and cosmic shear datasets are in tension in the standard

Λ

Cold Dark Matter (

Λ

CDM) model, and that adding massive neutrinos does not relieve the tension. If we include an additional scaling parameter on the CMB lensing amplitude

A_{l e n s}

, we find that this can put in agreement the Planck 2015 with the cosmic shear data.

A_{l e n s}

is a phenomenological parameter that is found to be more than

2 σ

higher than the expected value in the Planck 2015 data, suggesting an higher amount of lensing in the power spectra, not supported by the trispectrum analysis. Full article

(This article belongs to the Special Issue Anomalies and Tensions of the Cosmic Microwave Background)

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Anomalies and Tensions of the Cosmic Microwave Background

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