• Physics and Astronomy Colloquium

February 2, 2024 3:30 PM
PAIS 1100

Host:

Rouzbeh Allahverdi

Presenter:

Dr. Subir Sarkar (Oxford)

Video Recording

In the ΛCDM cosmological model the Universe is assumed to be isotropic and homogeneous, when averaged on large scales. That the cosmic microwave background (CMB) has a dipole anisotropy is interpreted as due to our peculiar (non-Hubble) motion because of local inhomogeneity. There must then be a corresponding dipole in the sky distribution of sources at high redshift. Using catalogues of radio sources and quasars we find that this expectation is rejected at >5σ, i.e. the distribution of distant matter is not isotropic in the 'CMB frame’. This calls into question the standard practice of boosting to this frame for analysing cosmological data, in particular to infer an (isotropic) acceleration of the Hubble expansion rate from Type Ia supernovae, which is interpreted as due to a Cosmological Constant Λ.