This workshop is part of the Bernoulli Center programme at EPFL, to be held from 18 to 22 May 2026.

We will explore the following open questions in theoretical cosmology, related to the quantisation of gravity:

1. How does one describe gauge-invariant observables in quantum gravity that resemble measurements carried out by an observer residing in the spacetime (such as ourselves)?
2. Should effects of topology change (spacetimes with wormholes) be considered? Which wormhole spacetimes contribute to physical observables in quantum gravity?
3. Important contributions to observables can originate from “complexified” spacetimes. A key example is the Hartle-Hawking geometry which contributes to the wavefunction of the universe. Can we formulate a general principle for which complex saddles contribute, and which do not?

The goal of this workshop is to bring together a representative part of the research community responsible for recent progress on these questions, which spans several fields.