Inflationary Cosmology from Anti-de Sitter Wormholes

We propose a new type of wave function for the Universe computed from the Euclidean path integral, with asymptotically anti-de Sitter (AdS) boundary conditions. In the semiclassical limit, it describes a Euclidean (half-)wormhole geometry, exhibiting a local maximum of the scale factor at the surface of reflection symmetry, giving rise to an expanding Universe upon analytic continuation to Lorentzian signature. We find that these Euclidean wormholes set natural initial conditions for inflation and that the semiclassical Wheeler-DeWitt wave function can favor a long-lasting inflationary epoch, resolving a wellknown issue of the no-boundary proposal. Because of the asymptotic AdS conditions in the Euclidean past, they raise the possibility of describing the physics of inflating cosmologies and their perturbations within the context of holography.