Quantum gravity and the measurement problem in quantum mechanics

TL;DR

The paper argues that integrating gravity into quantum mechanics reshapes the measurement problem by leveraging holography and the island rule, which together imply a closed-universe Hilbert space with $\dim \mathcal{H}_{\text{universe}} = 1$, potentially removing the need for wavefunction collapse at the universal scale. It also shows that gravity introduces observer-dependent algebras and edge modes, linking nontrivial subsystem physics to a globally trivial Hilbert space under certain topologies. By connecting the Page curve, unitarity in black hole evaporation, and Hamiltonian constraints, the work suggests that the universe’s topology plays a fundamental role in quantum foundations. Overall, gravity may resolve core measurement problems and requires a gravity-aware formulation of observables and subsystems, with topology guiding consistency requirements.

Abstract

The measurement problem in quantum mechanics is almost exclusively discussed in situations where gravity is ignored. We discuss some recent developments in our understanding of quantum gravity and argue that they significantly alter the problem. Quantum gravity may even resolve one of the thorniest questions in discussions of the measurement problem: who collapses the wavefunction of the entire universe?

Figures (1)

• Figure 1: Who collapses the wavefunction of the entire universe? Figure due to John Wheelerwheeler1980beyond.