In my presentation I discuss recent progress in search for new Euclidean wormhole solutions, a topic which is based on research started with Valery Rubakov and Peter Tinyakov back in 1988. In current study we investigate extension of axion gravity (studied by Giddings and Strominger), with an extra massive dilaton field or scalar field with symmetric double well potential. We found that in both theories new types of wormhole solutions exist and investigated their properties as a function of parameters of the model (axion charge, dilatonic coupling constant etc.) Euclidean actions of these new wormholes are typically comparable with actions of Giddings-Strominger type wormholes. These new types of wormholes are leading to expanding baby universes after analytic continuation back to Minkowski signature, whereas Giddings-Strominger wormholes are leading to contracting baby universes.
In addition rich structures of generalized Giddings-Strominger wormholes are found in axion gravity with massive dilaton. Presentation is based on a recent new results obtained in 2023 in collaboration with Caroline Jonas and Jean-Luc Lehners.