The interacting multiverse and its effect on the cosmic microwave
  background
  We study a toy model of a multiverse consisting of canonically quantized
universes that interact with each other on a quantum level based on a
field-theoretical formulation of the Wheeler-DeWitt equation. This interaction
leads to the appearance of a pre-inflationary phase in the evolution of the
individual universes. We analyze scalar perturbations within the model and
calculate the influence of the pre-inflationary phase onto the power spectrum
of these perturbations. The result is that there is a suppression of power on
large scales, which can describe well the Planck 2018 data for the cosmic
microwave background anisotropies and could thus indicate a possible solution
to the observed quadrupole discrepancy.
