One more question: it appears that portions of the universe are expanding away from us faster than the speed of light. Given this, particles in two 'parts' of the universe that are no longer causally connected should not be able to influence each other (due to speed of light constraint). So, say I have an electron sitting happily in one part of the universe and a proton in that moves into a portion of space receding from the electron at a speed faster than light. Now, the quantum wave function for each particle should occupy all of spacetime, and so when I compute the path integral, in theory, I should include terms for the electron and the proton interacting - however, any measurable interaction would violate relativity (by transmitting information). So, is it the case that the relevant terms in the path integral 'cancel' in some way, such that relativity is respected? Thanks!