There is no room for a physical collapse or, on the contrary, for an ad hoc privileged role of conscious observers; the wave functions only predict the probabilities but they can be calculated for any set of consistent histories, regardless of whether the systems look conscious, unconscious, macroscopic, or microscopic; the only “collapse” that occurs is the rapid diagonalization of the density matrix in the preferred basis by the interactions with the environment; however, the “unrealized” diagonal entries of the matrix (probabilities of outcomes that won’t come true) are never “physically” set to zero because their interpretation always remains probabilistic, even when the classical approximation becomes acceptably accurate[.]

— Decoherence is a settled subject

— Lubos Motl

2015.02.19 Thursday ACHK