Emergence of classicality from an inhomogeneous quantum universe

Abstract: We give a short account of the quantisation of the Szekeres spacetime by considering the symmetries of a reduced action principle. This is an alternative approach than the one followed in the literature for the study of inhomogeneities, which is usually based on perturbations of an inhomogeneous field on the spacetime background. Here, we examine the emergence of classicality with an exact inhomogeneous solution. We check whether the two criteria for classicality are satisfied, that is the correlations on the phase space and decoherence. We verify that these two properties indeed hold, thus the classical behaviour emerges from our considerations. We comment on the connection between the emergence of an inhomogeneous spacetime and the current cosmological observations of a highly homogeneous universe at large scales.