The Copernican principle in light of the latest cosmological data

We pursue a program to confront observations with inhomogeneous extensions of the FLRW metric. The main idea is to test the Copernican principle (CP) rather than assuming it a priori. We consider the ACDM model endowed with a spherical ALTB inhomogeneity around us, that is, we assume isotropy and test the hypothesis of homogeneity. We confront the ALTB model with the latest available data from cosmic microwave background, BAO, type Ia supernovae, local H-0, cosmic chronometers, Compton y-distortion, and kinetic Sunyaev-Zeldovich effect. We find that these data can constrain tightly this extra inhomogeneity, almost to the cosmic variance level: on scales greater than or similar to 100 Mpc structures can have a small non-Copernican effective contrast of just delta(L)similar to 0.01. Furthermore, the constraints on the standard ACDM parameters are not weakened after marginalizing over the parameters that model the local structure, to which we assign ignorance priors. In other words, dropping the CP assumption does not imply worse constraints on the cosmological parameters. This positive result confirms that the present and future data can be meaningfully analyzed within the framework of inhomogeneous cosmology.

Automated summary

A program was pursued to test the Copernican principle by confronting observations with inhomogeneous extensions of the FLRW metric, which found that the extra inhomogeneity can be tightly constrained by current data without weakening the constraints on cosmological parameters. This positive result suggests that present and future data can be meaningfully analyzed within the framework of inhomogeneous cosmology.