The deceleration parameter in “tilted” Friedmann universes: Newtonian vs relativistic treatment

Tsagas, Christos G.; Kadiltzoglou, Miltiadis I.; Asvesta, Kerkyra

doi:10.1007/s10509-021-03995-7

Cited by 6 publications

(12 citation statements)

References 35 publications

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“…Note that we have set q = 1/2 in the above, which implies that expression (2.14) holds on an Einsteinde Sitter background. Having said that, we remind the reader that the above result applies to essentially all FRW backgrounds, irrespective of their spatial curvature and equation of state (see [67] and also footnote 1 here).…”

Section: Form Of the Peculiar Deceleration Parametermentioning

confidence: 89%

“…The relative-motion effects analysed here are not exclusive to the Einstein-de Sitter background, but apply to essentially all Friedmann-Robertson-Walker (FRW) backgrounds, irrespective of their spatial curvature and equation of state, including all those with matter that satisfies the strong-energy condition [66]. Also note that the effects are purely general relativistic in nature and cannot be naturally reproduced by a Newtonian study [67].…”

Section: Introductionmentioning

confidence: 86%

“…The extra input of the bulk-flow flux to the Einstein field equations feeds into the relativistic conservation laws and eventually emerges in the equations monitoring the linear evolution of the tilted cosmological model. More specifically, in a tilted almost-FRW universe with dust, expression (2.7) recasts into [56,67]…”

Section: Form Of the Peculiar Deceleration Parametermentioning

confidence: 99%

“…Note that ∆ describes inhomogeneities in the spatial distribution of the matter density and Z represents spatial variations in the universal expansion. 7 For more details and further discussion, the reader is referred to [56,67]. Before substituting (2.8) into Eq.…”

Section: Form Of the Peculiar Deceleration Parametermentioning

confidence: 99%

“…for the n-th harmonic [56,67]. Here, λ (n) is the physical scale of the peculiar-velocity perturbation (practically the size of the bulk flow), λ H = 1/H is the Hubble radius (quantifying the size of the observable universe, with λ H ≈ 4300 Mpc today) and λ K = a/|K| is the curvature scale of the FRW background (with K = ±1).…”

Section: Form Of the Peculiar Deceleration Parametermentioning

confidence: 99%

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Observational constraints on the deceleration parameter in a tilted universe

Asvesta,

Kazantzidis,

Perivolaropoulos

et al. 2022

Preprint

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We study a parametrization of the deceleration parameter in a tilted universe, namely a cosmological model equipped with two families of observers. The first family follows the smooth Hubble flow, while the second are the real observers residing in a typical galaxy inside a bulk flow and moving relative to the smooth Hubble expansion with finite peculiar velocity. We use the compilation of Type Ia Supernovae (SnIa) data, as described in the Pantheon dataset, to find the quality of fit to the data and study the redshift evolution of the deceleration parameter. In so doing, we consider two alternative scenarios, assuming that the bulk-flow observers live in the ΛCDM and in the Einstein-de Sitter universe. We show that a tilted Einstein-de Sitter model can reproduce the recent acceleration history of the universe, without the need of a cosmological constant or dark energy, by simply taking into account linear effects of peculiar motions. By means of a Markov Chain Monte Carlo (MCMC) method, we also constrain the magnitude and the uncertainties of the parameters of the two models. From our statistical analysis, we find that the tilted Einstein-de Sitter model, equipped with one or two additional parameters that describe the assumed large-scale velocity flows, performs similar to the standard ΛCDM paradigm in the context of model selection criteria (Akaike Information Criterion and Bayesian Information Criterion).

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Section: Form Of the Peculiar Deceleration Parametermentioning

confidence: 89%

Section: Introductionmentioning

confidence: 86%

Section: Form Of the Peculiar Deceleration Parametermentioning

confidence: 99%

Section: Form Of the Peculiar Deceleration Parametermentioning

confidence: 99%

Section: Form Of the Peculiar Deceleration Parametermentioning

confidence: 99%

See 3 more Smart Citations

Observational constraints on the deceleration parameter in a tilted universe

Asvesta,

Kazantzidis,

Perivolaropoulos

et al. 2022

Preprint

Self Cite

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Challenges for ΛCDM: An update

Perivolaropoulos

Skara

2022

New Astronomy Reviews

368

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Modelling the emergence of cosmic anisotropy from non-linear structures

Anton

Clifton

2023

Class. Quantum Grav.

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Astronomical observations suggest that the Universe may be anisotropic on the largest scales. In order to model this situation, we develop a new approach to cosmology that allows for large-scale anisotropy to emerge from the growth of non-linear structure. This is achieved by decomposing all relevant fields with respect to a preferred space-like direction, and then averaging the resulting scalar quantities over spatial domains. Our approach allows us to derive a set of large-scale effective field equations that govern the dynamics of any emergent large-scale anisotropy, and which (up to back-reaction terms) take the form of the field equations of the locally rotationally symmetric Bianchi cosmologies. We apply our approach to the dust-filled Farnsworth solutions, which are an interesting set of exact cosmological models that allow for both anisotropic expansion and large-scale bulk flow.

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The deceleration parameter in “tilted” Friedmann universes: Newtonian vs relativistic treatment

Cited by 6 publications

References 35 publications

Observational constraints on the deceleration parameter in a tilted universe

Observational constraints on the deceleration parameter in a tilted universe

Challenges for ΛCDM: An update

Modelling the emergence of cosmic anisotropy from non-linear structures

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