Spatial curvature endgame: Reaching the limit of curvature determination

Leonard, C. Danielle; Bull, Philip; Allison, Rupert

doi:10.1103/physrevd.94.023502

Cited by 34 publications

(40 citation statements)

References 88 publications

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“…A third possible way is to consider the PL18 constraint on Ω K as a, now reasonably unlikely, statistical fluctuation. Fortunately, future measurements will fully confirm or falsify current tensions and the PL18 evidence for curvature 56,57 . In the meantime, we argue that the tensions with ΛCDM present in the PL18 release should not be discarded merely as a statistical fluctuation but must be seriously investigated, since at face value they point towards a drastic rethinking of the current cosmological concordance model.…”

Section: It Is Interesting To Investigate If Astrophysical Measuremenmentioning

confidence: 81%

Planck evidence for a closed Universe and a possible crisis for cosmology

2019

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The recent Planck Legacy 2018 release has confirmed the presence of an enhanced lensing amplitude in CMB power spectra compared to that predicted in the standard ΛCDM model.A closed universe can provide a physical explanation for this effect, with the Planck CMB spectra now preferring a positive curvature at more than 99% C.L. Here we further investigate the evidence for a closed universe from Planck, showing that positive curvature naturally explains the anomalous lensing amplitude and demonstrating that it also removes a well-known tension within the Planck data set concerning the values of cosmological parameters derived at different angular scales. We show that since the Planck power spectra prefer a closed universe, discordances higher than generally estimated arise for most of the local cosmological observables, including BAO. The assumption of a flat universe could therefore mask a cosmological crisis where disparate observed properties of the Universe appear to be mutually inconsistent.Future measurements are needed to clarify whether the observed discordances are due to undetected systematics, or to new physics, or simply are a statistical fluctuation.The recent Planck Legacy 2018 release of observations of Cosmic Microwave Background (CMB) anisotropies (PL18, hereafter) has reported some unexpected results, revealing the possibility for new physics beyond the so-called ΛCDM standard cosmological model 1, 2 . Indeed, while the inflationary predictions for coherent acoustic oscillations have been fully confirmed, a preference for a higher lensing amplitude A lens than predicted in the base ΛCDM at about 3 standard deviations 1 arXiv:1911.02087v1 [astro-ph.CO] 5 Nov 2019 has been found in the temperature and polarization angular spectra. We argue that the "A lens " anomaly has profound implications for some extensions to ΛCDM such as the curvature of the universe. The constraints from the PL18 CMB spectra on curvature, parameterized through the energy density parameter Ω K , are indeed quite surprising, suggesting a closed universe at 3.4 standard deviations (−0.007 > Ω K > −0.095 at 99% C.L. 1-3 ).As is well known, inflation theory naturally predicts a flat universe 4, 5 . However, inflationary models with Ω K < 0 6-8 are relatively simple to build, with primordial homogeneity and isotropy easier to achieve than in open models. An issue for closed inflation models is that to obtain Ω K ∼ −0.1, fine-tuning at a few per cent level is needed 7 . This does not sound very compelling, but it may still be acceptable given the presence of a far more finely-tuned cosmological constant.Closed models could also lead to a large-scale cut-off in the primordial density fluctuations, around the curvature scale R c = (c/H 0 )|Ω K | −0.5 ∼ 10 Gpc, in agreement with the observed low CMB anisotropy quadrupole 7, 9 . Confirmation of a positive spatial curvature would also have several implications for inflationary theory, and, for example, severely challenge models of eternal inflation 10, 11 .In this Letter, we show that, i...

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Section: It Is Interesting To Investigate If Astrophysical Measuremenmentioning

confidence: 81%

Planck evidence for a closed Universe and a possible crisis for cosmology

2019

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“…Other GR effects related to the behaviour of curvature in inhomogeneous spacetimes also contribute an apparent shift in the background cosmology. Given that current curvature upper limits are 1 or 2 orders of magnitude away from the level required to probe most of these effects, there is an imperative to continue pushing Ω k constraints to greater precision (i.e., to about 0.01% level) [21]. In addition, current standard measurements of the curvature parameter come from the combination of CMB and LSS, which does not take into account certain GR effects.…”

Section: Spatial Curvature In Cosmologymentioning

confidence: 99%

“…In particular, to test models of inflation such as eternal inflation, we need to reach the cosmic variance limit for spatial curvature [21].…”

Section: Spatial Curvature In Cosmologymentioning

confidence: 99%

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Data analysis and phenomenological cosmology

Coley¹,

Santos

Sanghai

2019

J. Cosmol. Astropart. Phys.

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In the era of precision cosmology, even percentage level effects are significant on cosmological observables. The recent tension between the local and global values of H 0 is much more significant than this, and any possible solution might rely on us going beyond the standard ΛCDM cosmological model. For much smaller, yet potentially significant effects, spatial curvature from averaging and cosmological backreaction on observational predictions could play a role. This is especially true with the higher precision of new observational data and improved statistical techniques. In this paper, we discuss the observational viability of a class of physically motivated cosmologies which can be parametrized by a phenomenological two-scale backreaction model with decoupled spatial curvature parameters and two Hubble scales. Using the latest JLA Supernovae data together with some of the latest BAO data, we perform a Bayesian model selection analysis and find that the phenomenological models are not favoured over the standard ΛCDM cosmological model. Although there is still a preference for non-zero and unequal dynamic and geometric spatial curvatures, there is little evidence for differing Hubble scales within these phenomenological template models.

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“…In fact other limitations, apart from those explained in the bulk of this communication might appear, namely there are at least two effects which, for the sake of simplicity, were neglected in this communication. The first one considers the eventual role of the spatial curvature Ω k in fixing constraints, due to the fact that Ω k = 0 can induce a time variation for the dark energy equation of state [19] and eventually distort the cosmological constraints as recently claimed in [20]. The second, additional limitations concerns other effects such as both gravitational and Doppler lensing [21], or even local gravitational redshifts [22], which may involve the appearance of extra scatters in the Hubble diagram, a fact which might degrade cosmological constraints as obtained from SNe Ia data analysis.…”

Section: Conclusion and Prospectsmentioning

confidence: 99%

Limitations of cosmography in extended theories of gravity

Cruz-Dombriz¹

2016

Proceedings of 11th International Workshop Dark Side of the Universe 2015 — PoS(DSU2015)

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The cosmographic approach, which only relies upon the homogeneity and isotropy of the Universe on large scales, has become an essential tool in dealing with an increasing number of theoretical possibilities for explaining the late-time acceleration of the Universe, ranging from Modified Gravity theories to Dark Energy alternatives passing from testing the cosmological concordance ΛCDM model. Despite its generality, we show that this method has a number of shortcomings when trying to adequately reconstruct theories with higher-order derivatives in either the gravitational or the matter sector. Herein some paradigmatic examples of such an inability, explanations of the limitations and prospective cures will be presented.

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Spatial curvature endgame: Reaching the limit of curvature determination

Cited by 34 publications

References 88 publications

Planck evidence for a closed Universe and a possible crisis for cosmology

Planck evidence for a closed Universe and a possible crisis for cosmology

Data analysis and phenomenological cosmology

Limitations of cosmography in extended theories of gravity

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