Quantum mechanics can unify with general relativity {quantum gravity}|. Quantum gravity is unitary.
gravity
Gravity curves space-time, and space-time determines mass motions {Wheeler-DeWitt equation}. Gravitons and interactions among gravitons determine curvature, but interactions are small if curvature is much larger than Planck length. Interactions take all possible paths, because no information is available about interaction.
gravity: metrics
For cosmology, measurements must be from within and so local. Metrics can have no singularities. Euclidean metrics can be local and can have two types, connected and disconnected.
Connected metrics are broad bounded space-time regions, with a local measurement region. Connected metrics have a boundary, and so boundary conditions. Connected metrics have few paths.
Disconnected metrics are compact unbounded space-time regions, with all local measurements. Disconnected metrics have no boundary, and so no boundary conditions. Disconnected metrics have almost all paths.
wavefunction
Universe wavefunction determines particle positions and depends on three spatial-dimension metrics and on particle. It does not depend on time, because compact metric has no preferred time. It does not depend on coordinate choice, becasue coordinates are equivalent.
Observers can see only part of space, so universe has mixed quantum state, which implies decoherence and classical physics. Superpositions do not happen, because gravitational effects cancel superpositions.
Physical Sciences>Physics>Quantum Mechanics>Theory>Quantum Relativity>Theories
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Date Modified: 2022.0224