One bubble to rule them all

Abstract

We apply the principles of quantum mechanics and quantum cosmology to predict probabilities for our local observations of a Universe undergoing false-vacuum eternal inflation. At a sufficiently fine-grained level, histories of the Universe describe a mosaic of bubble universes separated by inflationary regions. We show that predictions for local observations can be obtained directly from sets of much coarser-grained histories which only follow a single bubble. These coarse-grained histories contain neither information about our unobservable location nor about the unobservable large-scale structure outside our own bubble. Applied to a landscape of false vacua in the no-boundary state, we predict our local Universe emerged from the dominant decay channel of the lowest-energy false vacuum. We compare and contrast this framework for prediction based on quantum cosmology with traditional approaches to the measure problem in cosmology.