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Matter as Excitation of Fields: Model or Reality?

  1. Dec 15, 2012 #1
    Are SM particles expected to really be i) simple excitations of their associated fields, ii) particulate matter which happens to be very conveniently (and precisely) modeled as excitations of such fields or iii) we can't judge one way or the other in the present state of our knowledge?

    If they are excitations of fields, can we still talk of matter as such or does everything become either i) extended low-energy 'macro' field space or ii) very high-energy localised 'micro' field space (in lieu of matter)?

    Last edited: Dec 15, 2012
  2. jcsd
  3. Dec 15, 2012 #2


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    Our present state of knowledge suggests that it doesn't matter. We only understand reality via models. We can't say what is "really" going on, only that what's happening fits or doesn't fit particular models.
  4. Dec 15, 2012 #3


    Staff: Mentor

    Science is about models and correspondence with experiment. It is a philosophical question if that tells us about reality whatever that is. I believe it does but philosophers have argued it to death without arriving at a definite answer. The practice of science however is pretty much ambivalent to it.

    I personally side with Weinberg, as I suspect most scientists do (not that I classify myself as a scientist - merely a guy who is fortunate in having a background in math and an interest):
    'All this is wormwood to scientists like myself, who think the task of science is to bring us closer and closer to objective truth.'

    Whats the current paradigm? Depends on you view of string theory - I am a believer and think that's what nature is at rock bottom - as one string guy says all roads lead to string theory - but not everyone agrees. I also believe QM whispers in your ear something more is going on and what that something is may became clearer over time - or may not.

    Last edited: Dec 15, 2012
  5. Dec 16, 2012 #4
    Somehow several comments here were lost?

    I suppose you did not want to hear arguments (bickering) about strings...
    So here is my take on the question. Consider the em field (or photon field).
    On the one hand, we have excitations of this field that correspond to well-defined quanta (photons) of energy, as we can see when we look at absorption etc. The general state of a photon field may contain an uncertain number of photons (in a coherent state), so it can be in a superposition of different photon number states. If we use the formalism of Feynman diagrams, we can nevertheless describe most phenomena uing the picture of exchanged particles, but we must not forget that reality is a quantum-mechanical superposition of these possibilities.
    So if you want, you can use the particle picture.
    OTOH, you can describe everything with fields as well - a classical state of the photon field has a well-defined value at every point. Again, the general state is a superposition of all these possible states (and you can calculate things using "path integrals" that are in reality field configuration integrals).
    So either fields or particles can be used as "basis" of your description - you need superpositions in any case to describe a general state. Both views are equivalent, so you can take your pick. It's a bit as if you were asking in classical mechanics: Does nature behave according to Newtons axioms or to the Lagrangian principle? Both descriptions are correct.
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