Cosmological Parameters Are Dressed

Buchert, Thomas; Carfora, Mauro

doi:10.1103/physrevlett.90.031101

Cited by 114 publications

(175 citation statements)

References 11 publications

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“…Similar ideas have actually been held in other contexts [84,85], and in particular regarding the spatial curvature [86,87]. We claim that the simplest Swiss-cheese models are good models to address such questions-as well as the RicciWeyl problem and the fluid approximation-with their own use, between the perturbation theory and N -body simulations.…”

Section: Discussionmentioning

confidence: 80%

Interpretation of the Hubble diagram in a nonhomogeneous universe

Fleury¹,

Dupuy²,

Uzan³

2013

Phys. Rev. D

130

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In the standard cosmological framework, the Hubble diagram is interpreted by assuming that the light emitted by standard candles propagates in a spatially homogeneous and isotropic spacetime. However, the light from "point sources"-such as supernovae-probes the Universe on scales where the homogeneity principle is no longer valid. Inhomogeneities are expected to induce a bias and a dispersion of the Hubble diagram. This is investigated by considering a Swiss-cheese cosmological model, which (1) is an exact solution of the Einstein field equations, (2) is strongly inhomogeneous on small scales, but (3) has the same expansion history as a strictly homogeneous and isotropic universe. By simulating Hubble diagrams in such models, we quantify the influence of inhomogeneities on the measurement of the cosmological parameters. Though significant in general, the effects reduce drastically for a universe dominated by the cosmological constant.

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Section: Discussionmentioning

confidence: 80%

Interpretation of the Hubble diagram in a nonhomogeneous universe

Fleury¹,

Dupuy²,

Uzan³

2013

Phys. Rev. D

130

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“…It is interesting to note that the backreaction of cosmological fluctuations may cause effective non-zero curvature that may yield practical limits on our ability to measure w(z) accurately at z > 1 (see e.g. [18]). …”

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confidence: 99%

Dynamical dark energy or simply cosmic curvature?

Clarkson

Cortês

Bassett

2007

J. Cosmol. Astropart. Phys.

201

265

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We show that the assumption of a flat universe induces critically large errors in reconstructing the dark energy equation of state at z 0.9 even if the true cosmic curvature is very small, O(1%) or less. The spuriously reconstructed w(z) shows a range of unusual behaviour, including crossing of the phantom divide and mimicking of standard tracking quintessence models. For 1% curvature and ΛCDM, the error in w grows rapidly above z ∼ 0.9 reaching (50%, 100%) by redshifts of (2.5, 2.9) respectively, due to the long cosmological lever arm. Interestingly, the w(z) reconstructed from distance data and Hubble rate measurements have opposite trends due to the asymmetric influence of the curved geodesics. These results show that including curvature as a free parameter is imperative in any future analyses attempting to pin down the dynamics of dark energy, especially at moderate or high redshifts.Introduction The quest to distinguish between a cosmological constant, dynamical dark energy and modified gravity has become the dominant obsession in cosmology. Formally elevated to the status of one of the most important problems in fundamental physics, [22] [23] uncovering the true nature of dark energy, as encapsulated in the ratio of its pressure to density, w(z) = p DE /ρ DE , has become the focus of multi-billion dollar proposed experiments using a wide variety of methods, many at redshifts above unity (see e.g. [1]).Unfortunately these experiments will only measure a meagre number of w(z) parameters to any precisionperhaps two or three [3] [24] -since the standard methods all involve integrals over w(z) and typically suffer from subtle systematic effects. As a result of this information limit, studies of dark energy have traditionally fallen into two groups. The first group (see e.g. [10]) have taken their parameters to include (Ω m , Ω DE , w) with w constant and often set to −1. The 2nd group are interested in dynamical dark energy and have typically assumed Ω k = 0 for simplicity while concentrating on constraining w(z) parameters (see e.g. [11] ) [25].In retrospect, the origins of the common practise of ignoring curvature in studies of dynamical dark energy are clear. Firstly, the curved geodesics add an unwelcome complexity to the analysis that has typically been ignored in favour of studies of different parametrisations of w(z). Secondly, standard analysis of the Cosmic Microwave Background (CMB) and Baryon Acoustic Oscillations (BAO) in the context of adiabatic ΛCDM also put stringent limits on the curvature parameter, e.g. Ω k = −0.003 ± 0.010 from WMAP + SDSS [12,13]. As a result it was taken for granted that the impact on the reconstructed w(z) would then be proportional to Ω k and hence small compared to experimental errors.Further support for the view that Ω k should not be included in studies of dark energy came from informa-

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“…The third alternative is that we might not be applying the theory correctly or beyond its realm of validity. Namely, even though effects that go beyond general relativity (GR) or its Newtonian limit are small locally, they may accumulate over large distances and/or through averaging, see [5][6][7] for various approaches that advocate this idea and implement it in different ways. In this Letter we advocate a new approach to describe gravity at large distances that is agnostic about the issue which of these three alternatives is realized in Nature.…”

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confidence: 99%

Erratum: Model for Gravity at Large Distances [Phys. Rev. Lett.105, 211303 (2010)]

Grumiller¹

2011

Phys. Rev. Lett.

108

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We construct an effective model for gravity of a central object at large scales. To leading order in the large radius expansion we find a cosmological constant, a Rindler acceleration, a term that sets the physical scales and subleading terms. All these terms are expected from general relativity, except for the Rindler term. The latter leads to an anomalous acceleration in geodesics of test-particles. 95.35.+d, Gravity at large distances poses some of the most difficult puzzles in contemporary gravitational physics. The cosmological constant problem [1] and the nature of dark matter [2] are the most prominent ones. At a somewhat smaller scale, both in terms of actual size and in terms of scientific credibility, there are fly-by anomalies [3] and the Pioneer anomaly [4]. The word "anomalous" here refers to the difference between the observed trajectory of a test-particle in the gravitational field of a central object and the calculated trajectory. The pair test-particle/central object can mean e.g. galaxy/cluster, star/galaxy, Sun/Pioneer spacecraft, Earth/satellite, etc.Conceptually, there are three ways to resolve the anomalies. Either we modify the matter content of the theory (dark matter), or we modify the gravitational theory itself. The third alternative is that we might not be applying the theory correctly or beyond its realm of validity. Namely, even though effects that go beyond general relativity (GR) or its Newtonian limit are small locally, they may accumulate over large distances and/or through averaging, see [5][6][7] for various approaches that advocate this idea and implement it in different ways. In this Letter we advocate a new approach to describe gravity at large distances that is agnostic about the issue which of these three alternatives is realized in Nature. The main strength of our method lies in its rigidity -there is only one new free parameter -and in its ab initio nature.One well-established key ingredient to our approach is to construct an effective field theory by writing down the most general action consistent with all the required symmetries and with additional assumptions (power counting renormalizability, analyticity, ...). A crucial point is that we impose spherical symmetry in addition to diffeomorphism invariance, which often is a good approximation in the IR [27]. Spherical symmetry effectively reduces the theory to two dimensions. The main result of this Letter is that the most general action consistent with our assumptions leads to an additional term in the gravitational potential as compared to GR. This novel term generates accelerations similar to the ones observed in various "anomalous" systems in Nature and has a beautifully simple geometric interpretation as Rindler acceleration. EFFECTIVE FIELD THEORY FOR IR GRAVITYTo address the issue of anomalous acceleration of testparticles in the gravitational field of a central object we first simplify the underlying theory as much as possible. We assume that spacetime is described by a spherically symmetric metric in four dim...

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Cosmological Parameters Are Dressed

Cited by 114 publications

References 11 publications

Interpretation of the Hubble diagram in a nonhomogeneous universe

Interpretation of the Hubble diagram in a nonhomogeneous universe

Dynamical dark energy or simply cosmic curvature?

Erratum: Model for Gravity at Large Distances [Phys. Rev. Lett.105, 211303 (2010)]

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