Everett's "Relative State Formulation of Quantum Mechanics" (RSQM), which appeared in Reviews of Modern Physics, is based on his thesis "The Theory of the Universal Wavefunction". The most noteworthy property of these works is the claim by other authors that these works are the seminal contribution to Many Worlds theories of branching realities and the claim that practical laboratory experimental tests of RSQM are not possible. This report shows that Everett's two works describe a formulation of quantum mechanics that contradicts an overwhelming body of experimental physics.
Abstract This chapter provides a detailed explanation of Everett's three works — his thesis “On the Foundations of Quantum Mechanics”, a short paper entitled “‘Relative State’ Formulation of Quantum Mechanics”, and a long paper “The Theory of the Universal Wave Function”. It also discusses what was wrong with von Neumann's theory. It evaluates five alternatives presented by Everett for developing a satisfactory formulation of quantum mechanics. It provides an explanation for Everett's interpretation of pure wave mechanics and his principle of the relativity of states. Lastly, it evaluates the classical appearance and behaviour of macroscopic systems.
Everett wanted a formulation of quantum mechanics that (i) took the linear dynamics to be a complete and accurate description of the time-evolution of all physical systems and (ii) logically entailed the same subjective appearances predicted by the standard formulation of quantum mechanics. While most everyone would agree with this description of Everett's project, there is little agreement on exactly how his relative-state formulation was supposed to work. In this paper, I consider two very different readings of Everett: the bare reading and the splitting-worlds reading. What distinguishes these is their interpretation of the wave function and how one accounts for the experiences of observers. The difficulty in interpreting Everett, however, is illustrated by the fact that neither reading is entirely compatible with his own description of his project.