Parameter Independence and Outcome Independence in Dynamical Collapse Theories

Abstract

Ghirardi, Grassi, Butterfield, and Fleming have previously argued that two distinct formulations of dynamical reduction (GRW) theories have distinct non-local properties: one (the "non-linear" formulation) violates Parameter Independence while the other (the "linear + cooking" formulation) violates Outcome Independence. The claim is then that, since theories violating Outcome Independence are compatible with relativity in a way that theories violating Parameter Independence are not, the "linear + cooking" dynamical reduction theories hold the key to reconciling quantum non-locality with relativity. I review and assess this claim, arguing that, while ultimately misleading, there is an interesting and important lesson to be extracted.