Peculiar motions, accelerated expansion and the cosmological axis

Abstract

Peculiar velocities change the expansion rate of any observer moving relative to the smooth Hubble flow. As a result, observers in a galaxy like our Milky Way can experience accelerated expansion within a globally decelerating universe, even when the drift velocities are small. The effect is local, but the affected scales can be large enough to give the false impression that the whole cosmos has recently entered an accelerating phase. Generally, peculiar velocities are also associated with dipole-like anisotropies, triggered by the fact that they introduce a preferred spatial direction. This implies that observers experiencing locally accelerated expansion, as a result of their own drift motion, may also find that the acceleration is maximised in one direction and minimised in the opposite. We argue that, typically, such a dipole anisotropy should be relatively small and the axis should probably lie fairly close to the one seen in the spectrum of the Cosmic Microwave Background.

Typos corrected. Published version

References in corpus (10)

• Relativistic cosmology and large-scale structure
• Time drift of cosmological redshifts as a test of the Copernican principle
• Living in a Void: Testing the Copernican Principle with Distant Supernovae
• Looking the void in the eyes - the kSZ effect in LTB models
• What is dust? - Physical foundations of the averaging problem in cosmology
• Backreaction: directions of progress
• Scale dependence of cosmological backreaction
• Toward physical cosmology: focus on inhomogeneous geometry and its non-perturbative effects
• Is backreaction really small within concordance cosmology?
• Six Puzzles for LCDM Cosmology

Cited by in corpus (27)

• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• Is the Observable Universe Consistent with the Cosmological Principle?
• Evidence for anisotropy of cosmic acceleration
• Probing cosmic anisotropy with gravitational waves as standard sirens
• Constraining the Anisotropic Expansion of Universe
• Direction Dependence of the Deceleration Parameter
• Observational constraints on the deceleration parameter in a tilted universe
• Testing spatial curvature and anisotropic expansion on top of the $\Lambda$CDM model
• Multipole decomposition of the general luminosity distance 'Hubble law' -- a new framework for observational cosmology
• The deceleration parameter in `tilted' Friedmann universes
• Redshift drift as a model independent probe of dark energy
• Testing $\Lambda$CDM cosmology in a binned universe: anomalies in the deceleration parameter
• Coarse-grained description of cosmic structure from Szekeres models
• The peculiar Raychaudhuri equation
• Constraining the local variance of $H_0$ from directional analyses
• The deceleration parameter in `tilted' universes: generalising the Friedmann background
• Gravitationally influenced particle creation models and late-time cosmic acceleration
• Late Time Cosmological Evolution in f(R) theories with Ordinary and Collisional Matter
• Anisotropy in Pantheon+ supernovae
• Dark matter, a new proof of the predictive power of general relativity
• Peculiar velocity measurement in a clumpy universe
• Modelling the emergence of cosmic anisotropy from non-linear structures
• Dark Energy or local acceleration?
• 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
• A fractal LTB model cannot explain Dark Energy
• Supernovae as cosmological probes