The Quantum Formalism and the GRW Formalism

TL;DR

This paper introduces the GRW formalism, a framework that summarizes the empirical predictions of the GRW theories of wave function collapse, highlighting differences from standard quantum mechanics and limitations on measurable quantities.

Contribution

It provides the first succinct formalism for calculating testable predictions of GRWm and GRWf, akin to the quantum formalism but with different operators.

Findings

The GRW formalism parallels the quantum formalism in structure.

It enables direct computation of empirical predictions for GRWm and GRWf.

Some quantities cannot be measured within the GRW theories.

Abstract

The Ghirardi-Rimini-Weber (GRW) theory of spontaneous wave function collapse is known to provide a quantum theory without observers, in fact two different ones by using either the matter density ontology (GRWm) or the flash ontology (GRWf). Both theories are known to make predictions different from those of quantum mechanics, but the difference is so small that no decisive experiment can as yet be performed. While some testable deviations from quantum mechanics have long been known, we provide here something that has until now been missing: a formalism that succinctly summarizes the empirical predictions of GRWm and GRWf. We call it the GRW formalism. Its structure is similar to that of the quantum formalism but involves different operators. In other words, we establish the validity of a general algorithm for directly computing the testable predictions of GRWm and GRWf. We further show that some well-defined quantities cannot be measured in a GRWm or GRWf world.