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confusion on quantum field theory

Are field quanta infinite in extent as stated in Art Hobsons paper? What does this even mean? I've not seen any electrons or atoms that are infinite in size?

Am I getting something wrong somewhere?

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marked as duplicate by Manishearth Jan 12 '13 at 14:30

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

he also says there energy is sometimes spread over light years? huh – lee hudson Jan 12 '13 at 13:37
Perhaps you should edit/update your earlier question (Confusion on quantum field theory) instead of asking a new one. – Wouter Jan 12 '13 at 14:16

According to QM, it is the probability amplitude who is "extended", not the observation point on a screen.

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so its the probability amplitude of the field quanta thats extended to infinite? not that the actual electron(field quanta) is infinite in size? Art Hobson clearly says the energy is spread over light years, what does this mean? – lee hudson Jan 12 '13 at 13:52
vladimar are you sure your not getting confused with QM by itself? this question is in regards to QFT and a field quanta being infinite in size. – lee hudson Jan 12 '13 at 13:58
Field quanta can be put made into arbitrary wavepackets, just like in QM. – Michael Brown Jan 12 '13 at 14:14
@MichaelBrown wavepackets of probability waves, no? – anna v Jan 12 '13 at 14:20
I was thinking something like $ \left|\Psi\right> = \int \mathrm{d}^d x f(x) \hat{\phi}^\dagger(x) \left|0\right>$, where $\hat{\phi}$ is a field and $f(x)$ is the spatial wavefunction. (Assuming free fields for simplicity.) – Michael Brown Jan 12 '13 at 14:24

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