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Spacetime in qm or qft

  1. Mar 12, 2015 #1
    spacetime is classical and continuous.. so when quantum system form superposition or entanglement, how is time treated esp in qft? how does spacetime keep track of the particles of fields? or how does the fields or particles able to jump in spacetime.. how is this handle in qm or qft?
  2. jcsd
  3. Mar 12, 2015 #2


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    Spacetime is classical and continuous in relativistic qft.
  4. Mar 12, 2015 #3
    but particles are connected to spacetime.. how can particles just appear and disappear anywhere in spacetime.. isn't it spacetime are supposed to where particles or fields can move
  5. Mar 12, 2015 #4


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    You should find quite a few discussions around this theme in the "Beyond the Standard Model" section (that is, if you are interested in treatments of spacetime in QFT beyond flat spacetime, not sure if this is the case).

    A paper that seems relevant is (copied from the biblio thread there)
    Fields as Bodies: a unified presentation of spacetime and internal gauge symmetry
    David Wallace
    (Submitted on 23 Feb 2015)
    Using the parametrised representation of field theory (in which the location in spacetime of a part of a field is itself represented by a map from the base manifold to Minkowski spacetime) I demonstrate that in both local and global cases, internal (Yang-Mills-type) and spacetime (Poincaré) symmetries can be treated precisely on a par, so that gravitational theories may be regarded as gauge theories in a completely standard sense.
  6. Mar 12, 2015 #5
    for now.. I just want to understand how qft deals with flat spacetime... so when the fields are in superposition, how did they treat the time and space in the equation, as superposition too? or did they untangle or separate the 2 (fields from and spacetime)?
  7. Mar 13, 2015 #6


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    The fields are not in superposition. In quantum theory, the field are observables, so they basically correspond to where classical observers can be in classical spacetime. There is still the quantum state which can be in superposition, and this state is not anywhere in space, but is in Hilbert space, and assigned to an entire surface of simultaneity.
  8. Mar 13, 2015 #7
    What is the difference between the quantum states in terms of eigenvalues etc between QM and QFT? For example, do we have the same position, momentum, energy? and why does QFT put operator in every point of space instead of values?
  9. Mar 14, 2015 #8
  10. Mar 14, 2015 #9
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