Speaker
Description
The existence of Euclidean wormholes contributing to the Euclidean path integral, and especially their (in)stability, is a long standing puzzle. It has implications both phenomenologically (by breaking the axion global shift symmetry, thus making it a possible dark matter candidate or large-field inflaton, and solving the strong CP-problem of QCD) and from a theoretical perspective, e.g. through the weak gravity conjecture. In this talk, I will describe a new type of Euclidean wormhole solutions in axion-gravity theories which lead to the nucleation of an expanding baby universe in Lorentzian time. This contrasts with the well-known Giddings-Strominger (GS) solutions that lead to a contracting baby universe in Lorentzian time. I will describe the key properties of these new solutions such as their action-to-charge ratio, and I will compare them to more standard GS-like wormhole solutions.
