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 rather than
assuming it a priori. We consider the $\Lambda$CDM model endowed with a
spherical $\Lambda$LTB inhomogeneity around us, that is, we assume isotropy and
test the hypothesis of homogeneity. We confront the $\Lambda$LTB model with the
latest available data from CMB, 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 $\gtrsim 100$ Mpc structures can have a
small non-Copernican effective contrast of just $\delta_L \sim 0.01$.
Furthermore, the constraints on the standard $\Lambda$CDM 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
Copernican principle 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.
