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In an earlier question, which was called a duplicate, I already asked a similar question. But I state my question differently now and add something to it.

Suppose "we" would reverse the direction of the motion of all elementary particles in the universe through phase-space, reverse the expansion of space (so not of spacetime for an obvious reason) as well as the development of all quantum fields associated with all the elementary particles in phase-space (so the particles are in fact not represented by points moving through phase-space, if we consider elementary particles as point-particles).

Does "doing" all these things (performing operations) amount to the reversal of time (somewhat like showing a film backward)? I know these operations differ from the time-reversal operator in QFT. I mean, doesn't the last one apply only to tiny parts of the universe (and certainly not to the entire wavefunction of the universe)? See for example here.

Deschele Schilder
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  • Maybe. "CPT-invariance" deals (among charge and parity) with time-reversal but what is meant by time reversal in CPT-invariance? It's defined by a time reversal operator so I don't think it is seen as I ask in my question. The operator certainly doesn't perform the operations I suggest. – Deschele Schilder Jan 06 '18 at 13:50
  • "as well as the development of all quantum fields", quantum field theory workd with CPT theorem and lorenz invariance. If your fantasy model has quantum fields, the answer is no. – anna v Jan 06 '18 at 14:44
  • Why? You can also reverse (in your imagination) the evolution of the wavefunction of one particle (in the position representation, the wave function would evolve to a wave function spreading out less and less), so why not that of a whole field of particles? – Deschele Schilder Jan 06 '18 at 16:21

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