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Pauli's exclusion principle?

  1. Aug 22, 2007 #1
    There must be a force repulsing the electrons for no more than two in the 1s state for example. What force is that?

    How is this principle connected to the HUP?
     
  2. jcsd
  3. Aug 22, 2007 #2
    There is no force behind the exclusion principle -- until you get to phenomenological models in condense matter theory, which occasionally postulates such a fictitious force. The exclusion principle is solely due to the spin-1/2 nature of electrons.
     
  4. Aug 22, 2007 #3

    dextercioby

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    And there's no connection with the HUP, since this follows from the axioms without considering the symmetrization/antisymmetrization of the state vector.
     
  5. Aug 22, 2007 #4

    malawi_glenn

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    As the others said, there is no force behind the Pauli principle. In fact, the pauli prinicple can be the SOURCE of force, degenerate pressure; in for example White dwarf stars, and neutron stars.
     
  6. Aug 23, 2007 #5
    I find that hard to believe. How then can particles know about the presence of the other?

    There must be messenger particles of somesort?
     
  7. Aug 23, 2007 #6
    So the HUP is more fundalmental?

    Is Pauli's exclusion principles derived experimentally or theoretically?
     
  8. Aug 23, 2007 #7

    malawi_glenn

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    Welcome to the world of Quantum mechanics! =)
     
  9. Aug 23, 2007 #8

    malawi_glenn

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    According to what I have learned (and my books do not mention anything else), it is derived theoretically. Just look it up in your QM books in the chapters on "Identical particles".



    And what do you mean "more fundamental", the HUP is also derived from theory, not so very difficult either.
     
  10. Aug 23, 2007 #9

    turbo

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    Pivoxa, it may help you to visualize the PEP this way. Imagine that a fermion is a condensation of the quantum vacuum field, and that the field has a "carrying capacity". In other words, the field cannot support the existence of two identical fermions in the same state. The fermions do not "know" where they are in relation to one another, nor do they repel one another - their failure to superimpose is a characteristic limitation of the field in which they arise. The existence of a fermion in a quantum state drives the probability of the existence of a same-spin twin in that same quantum state toward zero.
     
    Last edited: Aug 23, 2007
  11. Aug 23, 2007 #10
    All physics is experimental -- otherwise it's maths. The uncertainty principle is was a *principle* when Heisenberg proposed it, extrapolating on experimental evidence; now, we tend to derived it, as a consequence of the formalism (Hilbert spaces and projection operators). What is theoretical in one view is experimental in another. If you're serious about wanting to learn about quantum mechanics, get a good book -- I recommend Heisenberg's original, Physical Principles of Quantum Theory, which is a short and cheap book.
     
  12. Aug 23, 2007 #11

    dextercioby

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    No, the HUP is a consequence of the axioms, the Pauli exclusion principle is a conseqance of the axioms as well. Therefore none is more fundamental than the other.
     
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