Protective measurements and relativity of worlds

It is a fundamental and widely accepted assumption that a measure-ment result exists universally, and in particular, it exists for every ob-server, independently of whether the observer makes the measurement or knows the result. In this paper, we will argue that, based on an analysis of protective measurements, this assumption is rejected by the many-worlds interpretation of quantum mechanics, and worlds, if they indeed exist ac-cording to the interpretation, can only exist relative to systems which are decoherent with respect to the measurement result. In standard quantum mechanics, it is postulated that when the wave func-tion of a quantum system is measured by a macroscopic device, it no longer follows the linear Schrödinger equation, but instantaneously collapses to one of the wave functions that correspond to definite measurement results. However, this collapse postulate is ad hoc, and the theory does not tell us why and how a definite measurement result appears. This measurement problem is widel