Dear Forum, I have a question about inflation which has been bugging me for a while. Hopefully someone can help. During inflation, as a wavenumber k crosses the horizon, the quantum field mode associated with momentum k is supposed to "freeze in" as a classical perturbation, right? So, it seems like that mode of the field operator collapses into one particular eigenstate. And, when the mode re-crosses the horizon later on, it doesn't return to behaving as a quantum fluctuation - so the freezing seems to be irreversible. Does this mean that the freezing-in is like a measurement (in the sense of quantum mechanics), or is there another way to understand it? If it is a measurement, what does the measuring and when does it happen? If it isn't, then what am I getting wrong, above?