We propose a single algebraic constraint on physical Hilbert space: the total state |Ψ⟩ satisfies ⟨Ψ|Ω|Ψ⟩=1 for adistinguished self-adjoint operator Ω whose spectrum is bounded and whose unit eigenspace is one-dimensional.This constraint implies that the physical Hilbert space is effectively one-dimensional, resolving the measurement problemby eliminating branching at the fundamental level.
Vinness Aisingioro Ollervides (Mon,) studied this question.