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How can a free elementary particle really be a particle

  1. Dec 6, 2009 #1
    Free elementary particles are lighter than the Planck mass, how can the exist as particles, or are they just Compton particles having a Comton waveleght?
  2. jcsd
  3. Dec 6, 2009 #2


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    What is a "Compton particle"?
  4. Dec 6, 2009 #3
    What is a "Comton waveleght?"
  5. Dec 6, 2009 #4


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    Lots of things are lighter than the planck mass (which is not all that small at around 10^-8kg). I don't see how a planck mass has anything to do with particles being particles.
  6. Dec 7, 2009 #5
    Dear jtbell,

    Here I give you the background i used to pose my question.

    The Planck lenght is the smallest lenght one can physically attribute to a particle it corresponds to the smallest Schwarzschild blackhole which is physically possible.
    Blackholes have dimensions inverse proportional to their mass.
    To "particles" lighter than the Planck mass one can attribute a Compton wavelenght which is inverse proportional to their mass.
    In my question i gave them the name "Compton particle" because I have no better indication.
    Below I give you a description of the Compton wavelenght as you can find in Wikipedia

    From Wikipedia, the free encyclopedia
    The Compton wavelength is a quantum mechanical property of a particle. It was introduced by Arthur Compton in his explanation of the scattering of photons by electrons (a process known as Compton scattering). The Compton wavelength of a particle is equivalent to the wavelength of a photon whose energy is the same as the rest-mass energy of the particle.
  7. Dec 7, 2009 #6
    Correction: Of course it is proportional to its blackhole mass

  8. Dec 7, 2009 #7


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    You misunderstood something. The mass of the elementary particle has nothing to do with its wavelength.
  9. Dec 7, 2009 #8
    Dear Matterwave

    At the Planck mass Compton wavelenght and Schwarzchild radius are about equal. So I suppose at lower mass free particles are compton waves.
    kind regards
    hurk 4
  10. Dec 7, 2009 #9
    Yes, it does. They are deeply related. Compton wavelength in planck units of length, and Compton frequency in planck units of time, are equal to the inverse of particle's mass in units of planck mass. Compton frequency is the native frequency of the particle, it is the frequency with which rest solutions of Dirac and Klein-Gordon oscillate.
  11. Dec 7, 2009 #10


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    This is all well and good, but I still don't understand what it has to do with anything.

    The "smallest wavelength", "highest point-like energy", etc all correspond to the Planck length/time/mass in various units.

    But this has nothing to do with the definition of the word "particle" - that comes from a detector: for example, when we shine a VERY low-intensity light at a florescent screen, we find that we see little "blips" that are isolated from each other. We interpret these as "particles" of light. The same experiment exists for electrons, neutrons, etc, suitably generalized.

    None of that has anything to do with Planck-anything!
  12. Dec 7, 2009 #11
    I said "free particle"
    Once it is located in your detector it is not free anymore and the compton wavelengh has gone. And in that situation I would not give it such a name like Compton particle.
    Maybe you can explain me what is wrong with this questioning?

    kind regards hurk4
  13. Dec 7, 2009 #12
    The source you are using is an interpretation based a belief that Plank's level is fundamental. This is the level usually associated with string theory.

    This is
    1) not a fact but a belief [not a well substantiated, but a problematic belief, see 2), 3) 4) ]

    2) the basis for this belief is not actually a requirement of string theory but certain versions of string theory. These versions of string theory all fail to produce the magnitude of gravity.

    3) is "disproved" by the versions of string theory that can produce the magnitude of gravity, which propose that space-time is bi-scalar [a solution to (conversely as implied by) the Hierarchy Problem].

    4) Planks scale theories produce a cosmological constant that is 10^128 times too large, bi.e 10^128 WRONG!!!! Not exactly an indorsement! (I may be off by a couple of powers of 10 but after 20 or 30 powers of 10 who cares).

    As indicated by the authors N. Arkani-Hamed, S. Dimpopoulus, and G. Dvali, [``The hierarchy problem and new dimensions at a millimeter'', Phys. Lett. B429 263-272 (1998)] the implication of a bi-scale string theory is that Planck scale is not a fundamental scale; its enormity is simply a consequence of the large size of the new dimensions.".

    It is the inter-scale interaction between the regular strings and
    the large strings that results in producing the weakness of
    gravity. Ignoring the bi-scale source of this weakness results in
    the false view that Plank's scale is fundamental.

    Also see, I. Antoniadis, N. Arkani-Hamed, S. Dimpopoulus, and G. Dvali, ``New dimensions at a millimeter to a fermi and superstrings at a TeV'', {\it Phys. Lett.} {\bf B}, {\bf 436} 257-263 (1998)
    Last edited: Dec 7, 2009
  14. Dec 8, 2009 #13
    Dear enotstrebor,
    Thank you for your post.
    It is not just in some of the string theories but it is also in other new theories like Loop Quantum Gravity that Planck units are used.
    In physics forums there are several extended threads discussing Planck units such as "Is the Plancklenght a commonly accepted theory or is it controversial anyway"? A nice answer I like is that of Marcus in his post nr.2.
    Or "How can the Planck lenght be claimed to be the smallest lenght"? etc. etc.

    Any way I must agree that Planck units are not experimentally verified but I would say that my convinction that they exist is more than just a belief. The Planck era IMO is a way to save physics from an unphysical singularity (even non realistic) and new theories like LQG are giving me hope that finaly we can realy go beyond a big bang started from an infinite small point at time zero.
    I will try to see and read your literature references.

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