Testing the Cosmological Principle

by Prof. Subir Sarkar (Rudolf Peierls Centre for Theoretical Physics, University of Oxford, UK)

Tuesday 11 May 2021, 12:00 → 14:00 Europe/Athens

In the standard 𝚲CDM model of cosmology it is assumed that the universe is statistically isotropic and homogeneous when averaged on scales exceeding ~100 Mpc. The large dipole anisotropy of the CMB is explained as due to our local peculiar motion because of inhomogeneities. This kinematic interpretation requires that there be a corresponding dipole in the angular distribution of high redshift objects. Using an  all-sky catalogue of 1.4 million quasars we find that this hypothesis is rejected at 4.9σ by the observed matter dipole. This calls into question the standard practice of boosting to the `CMB frame' to analyse cosmological data. In the heliocentric frame the acceleration of the Hubble expansion rate is also found to be anisotropic with 3.9σ confidence. It is thus no longer justifiable to make this acceleration look isotropic by boosting to the CMB frame and interpret it  as due to a Cosmological Constant.
[Astrophys. J. Lett. 908 (2021) L51; Astron. & Astrophys. 631 (2019) L19, arXiv:1808.04597]

 

Videoconference via https://us02web.zoom.us/j/83706184750

Subir_Sarkar_Part_1.mp4

Subir_Sarkar_Part_2.mp4

TestingCosmoPrinciple.pdf