ABSTRACT
My paper ‘How the measurement problem is an artefact of the mathematics’ begins, as Brigitte Falkenburg reports, from the assumption that sometimes superpositions turn into mixtures.1 If superpositions do turn into mixtures then some quantum evolutions must be describable by nonunitary Hamiltonians. It was typical at the time I wrote that paper to suppose that evolution described by a unitary Hamiltonian was the norm and evolution described by a nonunitary Hamiltonian was the exception that happens, if at all, only on measurement.
