Specify the Hamiltonian (dynamics) governing the universal quantum state

Develop an explicit Hamiltonian (or equivalent dynamical law) encoding the forces that operate in the universal quantum state, suitable for a full account of cosmic evolution in foundational interpretations and quantum cosmology.

Background

The proposal to identify possible worlds with Everettian branches presupposes a well-defined cosmic dynamics. The author notes that the Hamiltonian governing the universal state—the operator encoding the forces—has not been explicitly formulated.

This gap hinders precise statements about branching structure, decoherence, and the modal significance of branches.

References

Similarly, the proposal implies that the forces operating within the quantum cosmos (encoded in the Hamiltonian that, as I stressed in Chapters 4 and 5, nobody knows how to write down!) could not have been other than they are.

— The Multiverse: a Philosophical Introduction (2505.23639 - Butterfield, 29 May 2025) in Chapter 6, Section 3