Event description
Abstract: We will discuss the expectation value of the size of the universe in a cosmological context at a given time. I will mostly consider sine dilaton gravity, a toy model of 2d quantum cosmology. I will explain how to compute the sphere amplitude in sine dilaton, and the prediction it gives for the size of the universe. Much like the prediction by the no-boundary state in inflationary models, the sphere predicts a universe that is unrealistically small. I will then discuss the no-boundary proposal for closed universes with an observer. The observer's no-boundary state is dominated by a bra-ket wormhole and predicts a large universe, like our own.