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The deceleration parameter in ‘tilted’ universes: generalising the Friedmann background

Published version
Peer-reviewed

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Type

Article

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Authors

Tsagas, Christos G 

Abstract

jats:titleAbstract</jats:title>jats:pLarge-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.</jats:p>

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Keywords

Regular Article - Theoretical Physics

Journal Title

The European Physical Journal C

Conference Name

Journal ISSN

1434-6044
1434-6052

Volume Title

82

Publisher

Springer Science and Business Media LLC
Sponsorship
Hellenic Foundation for Research and Innovation (789)