Curvature versus distances: Testing the FLRW cosmology

Sapone, Domenico; Majerotto, Elisabetta; Nesseris, Savvas

doi:10.1103/physrevd.90.023012

Cited by 122 publications

(108 citation statements)

References 90 publications

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“…Redundancy -observing the same thing in different ways -is often invoked (and sold to the funding agencies) as a way to control systematics, but can also be used to perform effective null tests of ΛCDM predictions. A number of tests of fundamental assumptions such as the Copernican Principle and statistical homogeneity that use redundant distance and spatial curvature measurements have been proposed, for example [53,54,55,56].…”

Section: Observing Dark Energy In the Era Of Large Surveys Plenary Spmentioning

confidence: 99%

BeyondΛCDM: Problems, solutions, and the road ahead

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Akrami

Adamek

et al. 2016

Physics of the Dark Universe

444

210

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Despite its continued observational successes, there is a persistent (and growing) interest in extending cosmology beyond the standard model, ΛCDM. This is motivated by a range of apparently serious theoretical issues, involving such questions as the cosmological constant problem, the particle nature of dark matter, the validity of general relativity on large scales, the existence of anomalies in the CMB and on small scales, and the predictivity and testability of the inflationary paradigm. In this paper, we summarize the current status of ΛCDM as a physical theory, and review investigations into possible alternatives along a number of different lines, with a particular focus on highlighting the most promising directions. While the fundamental problems are proving reluctant to yield, the study of alternative cosmologies has led to considerable progress, with much more to come if hopes about forthcoming high-precision observations and new theoretical ideas are fulfilled.Keywords: cosmology -dark energy -cosmological constant problem -modified gravitydark matter -early universe Cosmology has been both blessed and cursed by the establishment of a standard model: ΛCDM. On the one hand, the model has turned out to be extremely predictive, explanatory, and observationally robust, providing us with a substantial understanding of the formation of large-scale structure, the state of the early Universe, and the cosmic abundance of different types of matter and energy. It has also survived an impressive battery of precision observational tests -anomalies are few and far between, and their significance is contentious where they do arise -and its predictions are continually being vindicated through the discovery of new effects (B-mode polarization [1] and lensing [2,3] of the cosmic microwave background (CMB), and the kinetic Sunyaev-Zel'dovich effect [4] being some recent examples). These are the hallmarks of a good and valuable physical theory.On the other hand, the model suffers from profound theoretical difficulties. The two largest contributions to the energy content at late times -cold dark matter (CDM) and the cosmological constant (Λ) -have entirely mysterious physical origins. CDM has so far evaded direct detection by laboratory experiments, and so the particle field responsible for it -presumably a manifestation of "beyond the standard model" particle physics -is unknown. Curious discrepancies also appear to exist between the predicted clustering properties of CDM on small scales and observations. The cosmological constant is even more puzzling, giving rise to quite simply the biggest problem in all of fundamental physics: the question of why Λ appears to take such an unnatural value [5,6,7]. Inflation, the theory of the very early Universe, has also been criticized for being fine-tuned and under-predictive [8], and appears to leave many problems either unsolved or fundamentally unresolvable. These problems are indicative of a crisis.From January 14th-17th 2015, we held a conference in Oslo, Norway to surve...

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Section: Observing Dark Energy In the Era Of Large Surveys Plenary Spmentioning

confidence: 99%

BeyondΛCDM: Problems, solutions, and the road ahead

Bull

Akrami

Adamek

et al. 2016

Physics of the Dark Universe

444

210

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“…Another advantage of the PCA is that there is no need to specify the cosmology; i.e. it is a model-independent approach, as the PCA will give us a set of functions that better describes the data [8], [9], [10], [11], [12], [13]. More details on the procedure of the PCA and the relevant sets of equations for each approach are also presented in Sec.…”

Section: Introductionmentioning

confidence: 99%

Comparison of piecewise-constant methods for dark energy

Nesseris

Sapone

2014

Phys. Rev. D

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We compare four different methods that can be used to analyze the type Ia supernovae (SnIa) data, ie to use piecewise-constant functions in terms of: the dark energy equation of state w(z), the deceleration parameter q(z), the Hubble parameter H(z) and finally the luminosity distance dL. These four quantities cover all aspects of the accelerating Universe, ie the phenomenological properties of dark energy, the expansion rate (first and second derivatives) of the Universe and the observations themselves. For the first two cases we also perform principal component analysis (PCA) so as to decorrelate the parameters, while for the last two cases we use novel analytic expressions to find the best-fit parameters. In order to test the methods we create mock SnIa data (2000 points, uniform in redshift z ∈ [0, 1.5]) for three fiducial cosmologies: the cosmological constant model (ΛCDM), a linear expansion of the dark energy equation of state parameter w(a) = w0 + wa(1 − a) and the Hu-Sawicki f (R) model. We find that if we focus on the two mainstream approaches for the PCA, i.e. w(z) and q(z), then the best piecewise-constant scheme is always w(z). Finally, to our knowledge the piecewise-constant method for H(z) is new in the literature, while for the rest three methods we present several new analytic expressions.PACS numbers: 95.36.+x, 98.80.Es

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“…What is particularly interesting for the coming decade are predictions for redshift evolution of Ω k , the average curvature parameter, from telescopes such as Euclid. Majerotto showed that statistically homogeneous and isotropic general-relativistic cosmological models in which the expansion rate history is observationally realistic, including the Timescape [40,99,100] and Tardis [45] models, have Ω k (z) relations that should be observationally distinguishable from ΛCDM to high significance by Euclid [95]. Both the models, as in the case of template metrics that match the supernovae type Ia distance-modulus-redshift relation, i.e., that of Ref.…”

Section: Recent Observational Resultsmentioning

confidence: 99%

“…Majerotto presented work together with Sapone and Nesseris [95] who applied the Clarkson, Bassett and Lu test [38,96] using eight H(z) cosmic chronometer estimates [97] (age of oldest passively evolving red galaxies at any given redshift z [98]) and a recent compilation of supernovae type Ia redshift-magnitude estimates. This test should distinguish some classes of relativistic or other non-FLRW models from the FLRW model.…”

Section: Recent Observational Resultsmentioning

confidence: 99%

Observational challenges for the standard FLRW model

Buchert

Coley

Kleinert

et al. 2016

Int. J. Mod. Phys. D

109

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We summarise some of the main observational challenges for the standard FriedmannLemaître-Robertson-Walker cosmological model and describe how results recently presented in the parallel session "Large-scale Structure and Statistics" (DE3) at the "Fourteenth Marcel Grossman Meeting on General Relativity" are related to these challenges.Keywords: large-scale structure; cosmic microwave background; statistics; generalrelativistic effects PACS numbers: 98.80.Es, 98.80.Jk, 95.36.+x, Observational Challenges for the ΛCDM ModelDespite the many well-known successes of the FLRW model with its standard parameter values, henceforth denoted the ΛCDM model, there is a wide range of observations with which it significantly disagrees. The statistical significance of these disagreements is very often debated from a Bayesian perspective. If the ΛCDM is accepted as being consistent with general relativity, then one must contend with a posteriori statistics, also called the look elsewhere effect, which globally requires ǎ Sidàk-Bonferonni correction [1] for assessing overall statistical significance. On the other hand, interpretation of structure formation within the ΛCDM model is to a large degree based on Newtonian physics-N -body simulations are widely seen as providing state-of-the-art ways of comparing the FLRW model to observational catalogues-but in comparison to general relativity, the former should be assigned an extremely weak prior.a Although precise tests of general relativity have led to * BFR: During invited lectureship. a For example, Keplerian orbits are disfavoured in relation to general-relativistic orbits at a significance level of more than 100σ [2] based on the periastron decay of the Hulse-Taylor pulsar B1913+16 [3] (See Fig. 2

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Curvature versus distances: Testing the FLRW cosmology

Cited by 122 publications

References 90 publications

BeyondΛCDM: Problems, solutions, and the road ahead

BeyondΛCDM: Problems, solutions, and the road ahead

Comparison of piecewise-constant methods for dark energy

Observational challenges for the standard FLRW model

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