Misc,

Spatially Homogeneous Universes with Late-Time Anisotropy

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(2022)cite arxiv:2212.03234.

Abstract

The Cosmological Principle asserts that on sufficiently large scales the universe is homogeneous and isotropic on spatial slices. Challenging this principle requires a departure from the FLRW ansatz. In this paper we analyse the cosmological evolution of spatially homogeneous but anisotropic universes in which only two of the three space dimensions are maximally symmetric, namely the closed Kantowski-Sachs universe and the open axisymmetric Bianchi type III universe. These models are characterised by two scale factors and we study their evolution in universes with radiation, matter and a cosmological constant. In all cases, the two scale factors evolve differently and this anisotropy leads to a lensing effect in the propagation of light. We derive explicit formulae for computing redshifts, angular diameter distances and luminosity distances and discuss the predictions of these models in relation to observations for type Ia supernovae and the CMB.

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