Abstract

Spontaneous localization (SL) is an alternative to standard quantum theory in which quantum state reduction is treated as a random physical process which is incorporated into the Schroedinger equation in an observer-independent way. We give a brief introduction to SL and a review of some proposed relativistic extensions. Based on these relativistic extensions we argue that for a single particle, non-relativistic SL should remain valid in the rest frame. This implies that relativistic calculations can be performed by transforming non relativistic results from the particle rest frame to the frame of an observer. We demonstrate this by considering a relativistic stream of non-interacting particles of cosmological origin and showing how their energy distribution evolves as a result of SL as they traverse the Universe. We present a solution and discuss the potential for astrophysical observations.