Beyond the Cosmological Standard Model

by Prof. Subir Sarkar (Oxford University)



The ΛCDM model is based on the assumption that the Universe is isotropic and homogeneous on large scales. That the CMB exhibits a large dipole anisotropy is explained as due to our `peculiar’ (non-Hubble) motion because of local inhomogeneities in the matter distribution. There should then be a corresponding dipole in the skymap of high redshift sources. We find however that the observed dipole in the distribution of of quasars does not match what is expected. This calls into question the standard practice of boosting to the `cosmic rest frame’ (in which the Universe is supposedly isotropic) to analyse cosmological data. In the heliocentric frame where observations are actually made, the acceleration of the Hubble expansion rate is also anisotropic. It cannot therefore be interpreted as due to a Cosmological Constant (vacuum energy) and is likely an artefact due to our being `non-Copernican’ observers.