  Given the collapse hypothesis (CH) of quantum measurement, EPR-type
correlations along with the hypothesis of the impossibility of superluminal
communication (ISC) have the effect of globalizing gross features of the
quantum formalism making them universally true. In particular, these hypotheses
imply that state transformations of density matrices must be linear and that
evolution which preserves purity of states must also be linear. A gedanken
experiment shows that lorentz covariance along with the second law of
thermodynamics imply a non-entropic version of ISC. Partial results using
quantum logic suggest, given ISC and a version of CH, a connection between
lorentz covariance and the covering law. These results show that standard
quantum mechanics is structurally unstable, and suggest that viable
relativistic alternatives must question CH. One may also speculate that some
features of the hilbert-space model of quantum mechanics have their origin in
space-time structure.
