  The Continuous Spontaneous Localisation (CSL) model solves the measurement
problem of standard quantum mechanics, by coupling the mass density of a
quantum system to a white-noise field. Since the mass density is not uniquely
defined in general relativity, this model is ambiguous when applied to
cosmology. We however show that most natural choices of the density contrast
already make current measurements of the cosmic microwave background
incompatible with other laboratory experiments.
