A deterministic Bell model

At the heart of the orthodox interpretation of the quantum theory is the measurement postulate. We recall the context in which this postulate has been introduced and why it is unsatisfactory 1 . It supposes that the wave-function is the complete description of a system of particles. If we assume that the wave-function evolves according to a linear equation, we face the problem of macroscopic superpositions (Schrödinger’s cat) 2 . Since those macroscopic superpositions are not observed, the measurement postulate is introduced, in order to stop the branching process somewhere, where systems encounter observers, who force them to collapse. By introducing the collapse, the world is split into two parts: a quantum world, made of systems, which can be in superpositions and are unable to perform measurements, and a classical world, made of observers, who on the contrary have the ability to cause a collapse and do not enter in superpositions. Systems are described by wave functions, whereas observers are described by positions. If one asks where the boundary between these two worlds is to be found or even why there is a boundary, the