Confronting the Cosmological Principle: Shaking the foundations of the Cosmos
by
Salle du conseil
IAP
This talk intends to put the Cosmological Principle (CP) to test by analyzing all-sky surveys of quasars and radio galaxies. CP asserts that the universe is isotropic and homogeneous on large scales. It attributes the Cosmic Microwave Background (CMB) thermal dipole to our local peculiar motion, hence giving it the name of kinematic dipole. If this attribution is correct, then all sky surveys of other cosmological probes should show a similar dipole in their distribution throughout the sky. More than forty years ago, researchers postulated the presence of a number count dipole in source distribution (dubbed as the matter dipole) as a test for the CP. However, recent research has found a disagreement between the matter dipole and kinematic dipole, with claims reaching well over 5σ! I will put the CP to test by analysis of all sky surveys of quasars and radio galaxies. Using Bayesian statistics, I will show that a dipole aligned with the CMB is present. However, the amplitude of the dipole is still in tension with our expectations, bringing the validity of the cosmological principle into question. We will also look into the future, discussing some outstanding issues in the domain and possible methods to increase the sophistication of the matter dipole test.