The deceleration parameter in `tilted' universes: generalising the Friedmann background

Abstract

Large-scale bulk peculiar motions introduce a characteristic length scale, inside which the local kinematics are dominated by peculiar-velocity perturbations rather than by the background Hubble expansion. Regions smaller than the aforementioned critical length, which typically varies between few hundred and several hundred Mpc, can be heavily "contaminated" by the observers' relative motion. For example, at the critical length -- hereafter referred to as the "transition scale", the sign of the locally measured deceleration parameter can change from positive to negative, while the surrounding universe is still decelerating globally. Overall, distant observers can assign very different values to their local deceleration parameters, entirely because of their relative motion. In practice, this suggests that information selected from regions inside and close to the transition scale hold only locally and they should not be readily extrapolated to the global universe. We show that this principle applies to essentially all Friedmann backgrounds, irrespective of their equation of state and spatial curvature. Put another way, the transition scale and the related effects are generic to linear peculiar-velocity perturbations. This study generalises previous work applied, primarily for reasons of mathematical simplicity, to a perturbed Einstein-de Sitter universe.

arXiv commentMinor revision, references added. To appear in EPJC

References in corpus (42)

• A 2.4% Determination of the Local Value of the Hubble Constant
• Planck 2018 results. I. Overview and the cosmological legacy of Planck
• Dipole Anisotropy in the COBE DMR First-Year Sky Maps
• A Test of the Cosmological Principle with Quasars
• Relativistic cosmology and large-scale structure
• Cosmic flows in the nearby universe from Type Ia Supernovae
• Evidence for anisotropy of cosmic acceleration
• Probing the anisotropic local universe and beyond with SNe Ia data
• Probing cosmic isotropy with a new X-ray galaxy cluster sample through the $L_{\text{X}}-T$ scaling relation
• Cosmic Flows on 100 Mpc/h Scales: Standardized Minimum Variance Bulk Flow, Shear and Octupole Moments
• Does Hubble Tension Signal a Breakdown in FLRW Cosmology?
• Cosmic radio dipole from NVSS and WENSS
• Searching for a Cosmological Preferred Axis: Union2 Data Analysis and Comparison with Other Probes
• Large peculiar motion of the solar system from the dipole anisotropy in sky brightness due to distant radio sources
• Dipoles in the Sky
• High redshift radio galaxies and divergence from the CMB dipole
• Probing the Cosmological Principle in the counts of radio galaxies at different frequencies
• The cosmological bulk flow: consistency with $\Lambda$CDM and $z\approx 0$ constraints on ${\sigma }_8$ and $\gamma$
• Revisiting the NVSS number count dipole
• Cosmological implications of the anisotropy of ten galaxy cluster scaling relations
• Hints of FLRW Breakdown from Supernovae
• The Cosmic Radio Dipole: Estimators and Frequency Dependence
• The 6dF Galaxy Survey: Bulk Flows on $50-70h^{-1}$ Mpc scales
• On Larger $H_0$ Values in the CMB Dipole Direction
• Dipole anisotropy in sky brightness and source count distribution in radio NVSS data
• Tilted Lemaitre-Tolman-Bondi Spacetimes: Hydrodynamic and Thermodynamic Properties
• Observational constraints on the deceleration parameter in a tilted universe
• Probing the anisotropic expansion from supernovae and GRBs in a model-independent way
• Probing Cosmological Isotropy With Type IA Supernovae
• Covariant velocity and density perturbations in quasi-Newtonian cosmologies
• Peculiar motions, accelerated expansion and the cosmological axis
• A new way to test the Cosmological Principle: measuring our peculiar velocity and the large scale anisotropy independently
• Does the Universe Accelerate Equally in all Directions?
• An estimation of local bulk flow with the maximum-likelihood method
• A large disparity in cosmic reference frames determined from the sky distributions of radio sources and the microwave background radiation
• Large angular scale multipoles at redshift ~0.8
• A relativistic approach to nonlinear peculiar velocities and the Zeldovich approximation
• The deceleration parameter in `tilted' Friedmann universes
• Field-level inference of galaxy intrinsic alignment from the SDSS-III BOSS survey
• Non-comoving Cold Dark Matter in a $\Lambda$CDM background
• Imprints of decaying dark matter on cosmic voids
• Testing the isotropy of the log N - log S slope for the NVSS radio catalogue

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• Anisotropy in Pantheon+ supernovae
• Big Bang in Dipole Cosmology
• Approximations for the divergence of the local large-scale structure velocity field and its implications for Tilted Cosmology
• Anisotropy in the cosmic acceleration inferred from supernovae
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