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Space-time continuity as an assumption in quantum theory

  1. Dec 20, 2013 #1
    There is an apparent conflict between relativity and quantum theory, in which case quantum theory must be redundant isn't it as it explicitly makes the assumption that spacetime is continuous whereas relativity in-fact derives the notion that spacetime is continuous from an experimentally observed aspect of constancy of speed of light. When a theory borrows the result of another theory as its foundation and then comes into conflict with the very theory from which it borrowed the idea,then doesn't logic tell that the lending theory is not complete or it's only partially correct and the borrowing theory is redundant. Its purely logical isn't it?
    Last edited: Dec 20, 2013
  2. jcsd
  3. Dec 20, 2013 #2


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    What if spacetime isn't continuous?
  4. Dec 20, 2013 #3
    i like the term.
    partially correct.

  5. Dec 20, 2013 #4
    That's a good question. If spacetime is not continuous then mass and energy cannot be discreet.
  6. Dec 20, 2013 #5
    Are we talking Loop Quantum Gravity? This is next on my list of important things to learn about before I die. Does anyone know of any decent sources?
  7. Dec 20, 2013 #6


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    Maybe start here: http://math.ucr.edu/home/baez/acm/ ?
  8. Dec 20, 2013 #7


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    Why? What does spacetime being continuous have to do with the apparent fact that mass is discretized?
  9. Dec 20, 2013 #8
    1st. There is no obvious conflict between relativity and quantum mechanics. There is an incomplete understanding of how to properly quantize general relativity, but that's not the same thing as saying there is conflict between them. For instance, Quantum Field Theory is both relativistic and quantized without any obvious conflicts.

    2nd. Even if there is a conflict between them, your logic doesn't seem to hold water. Quantum mechanics tenets go far beyond the assumption of continuous space time. The core of QM is the replacement of the dynamical variables with operators in some linear space (which space exactly depends on the details of the theory). You can't milk that out of relativity. there is no meaningful way in which relativity makes QM redundant
  10. Dec 20, 2013 #9


    Staff: Mentor

    There is no conflict:
    'Effective ï¬eld theory shows that general relativity and quantum mechanics work together perfectly normally over a range of scales and curvatures, including those relevant for the world that we see around us. However, effective ï¬eld theories are only valid over some range of scales. General relativity certainly does have problematic issues at extreme scales. There are important problems which the effective ï¬eld theory does not solve because they are beyond its range of validity. However, this means that the issue of quantum gravity is not what we thought it to be. Rather than a fundamental incompatibility of quantum mechanics and gravity, we are in the more familiar situation of needing a more complete theory beyond the range of their combined applicability. The usual marriage of general relativity and quantum mechanics is ï¬ne at ordinary energies, but we now seek to uncover the modiï¬cations that must be present in more extreme conditions. This is the modern view of the problem of quantum gravity, and it represents progress over the outdated view of the past.'

    Also be aware that all our theories, not just gravity, are thought to break down at the Plank scale - renormalizable or not.

  11. Dec 20, 2013 #10
    What if spacetime were in different structures connected through matter?
  12. Dec 20, 2013 #11
    imo both theories are partial correct
    maybe both replaced by a broader theory.
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