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I do not want answers telling me that wave-function collapse is not real and decoherence is the answer (I know the situation with that). I am asking a question purely on the basis if wave-function collapse is the correct method. My question is: in normal quantum mechanics superposition of the state (position, momentum) exists until the wave-function collapses (how or why it collapses is not important in this question), now in quantum field theory we can also have superposition as in the superposition of Fock space states with different particle number. Can the superposition also collapse here under collapse interpretations of quantum mechanics/quantum field theory?

Laymans answers would be mainly appreciated...

Hunter
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lee hudson
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    I downvoted the question because the OP imposes the condition that the right answer cannot be written down and wrong answers must be written instead. The interpretational issues of quantum mechanics are completely analogous in non-relativistic QM and in quantum field theory. The latter is just another example of a quantum theory, with a Hilbert space - that may be often mapped to the non-relativistic one - and some operators which are organized differently. There is no genuine collapse of anything in either theory, but if one imagines ones, it "works" completely analogously in QFT. – Luboš Motl Jan 19 '14 at 18:35
  • well whats the answer then? in collapse interpretations, does the superpostion of fock space states of particle number collapse? fock space states of particle number was never mentioned in 2013. whats the answer? – lee hudson Jan 19 '14 at 18:45
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    Some comments deleted. Others edited. Personal remarks will not be tolerated. Nor will attempts to control who can answer an question or to force the content of the answers. – dmckee --- ex-moderator kitten Jan 19 '14 at 18:48
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    @LubošMotl yep, as the OP explicitely stated what the answers should not say for him to deem them worthy, I voted to close as "primarly opinion based". In fact, it is not even a real question ... – Dilaton Jan 19 '14 at 22:07

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Quantum field theory does not have a special place within quantum mechanics as regards the Measurement Problem, or any of its proposed solutions. QFT is simply quantum mechanics when applied to a specific system, whose dynamical variables are the infinite degrees of freedom of a field. Just as in standard quantum mechanics, states are vectors in a Hilbert space (which can therefore be added together to give superposition states), and observables are operators on it. The collapse of a wavefunction - or its decoherence, or splitting off into different branches as it gets entangled with a measurement apparatus - looks exactly the same.

Emilio Pisanty
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    The same??? How does a photon collapse into a position eigenstate when it is measured? It rather disappears. Thus collapse needs modification in the relativistic case. See also http://physics.stackexchange.com/questions/193918 – Arnold Neumaier Nov 18 '15 at 11:20