On the uniqueness of the equation for state-vector collapse

TL;DR

This paper investigates the uniqueness of nonlinear wavefunction collapse models in quantum mechanics, establishing the most general class of continuous, no-faster-than-light signaling evolutions that could replace Schrödinger's equation.

Contribution

It identifies the broadest class of nonlinear, continuous wavefunction evolutions consistent with no-faster-than-light signaling, addressing the question of their uniqueness.

Findings

Most general class of continuous collapse models identified

Models compatible with no-faster-than-light signaling characterized

Addresses the uniqueness of nonlinear modifications to Schrödinger's equation

Abstract

The linearity of quantum mechanics leads, under the assumption that the wave function offers a complete description of reality, to grotesque situations famously known as Schroedinger's cat. Ways out are either adding elements of reality or replacing the linear evolution by a nonlinear one. Models of spontaneous wave function collapses took the latter path. The way such models are constructed leaves the question, whether such models are in some sense unique, i.e. whether the nonlinear equations replacing Schroedinger's equation, are uniquely determined as collapse equations. Various people worked on identifying the class of nonlinear modifications of the Schroedinger equation, compatible with general physical requirements. Here we identify the most general class of continuous wavefunction evolutions under the assumption of no-faster-than-light signalling.