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  1. May 17, 2007 #1


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    Why do we require tremendous energy (equivalent to the Planck's energy) to verify String/hyperspace/higherdimension theory?
  2. jcsd
  3. Jun 15, 2007 #2
    I have also wondered about this.

    I think the 'Introduction to loop quantum gravity' will help. Try dipping into the last page of the first post.

    The following is speculative:
    My explanation is that when the Kaluza metric is used with the GR Lagrangian you get the Plank Mass. Klein then went on to explain that you did not see the 5th dimension as it was so small etc.

    BUT if you use Kaluza metric with the simple Lagrangian* then the mass is the mass of electron (if you are considering an electron). It all comes down to simple calculations that an undergraduate student could do.

    The details are spelled out in
    Physics help & Math help - Physics forums > Physics > Special & General Relativity (Simple Kaluza Klein question)

    where I have shown that

    [tex] u^5 = d_{\tau}x^5 = (1 - A_{\alpha} u^{\alpha}q/m) [/tex]

    So [itex] x^5 \approx \tau [/itex].

    No one has said this explanation is on the right or wrong track yet - but this may be due to submitting my question in the wrong forum.

    * Lagrangian adapted from the super Hamiltonian, e.g. p 489 in Gravitation by Misner Thorne & Wheeler of 1970-1973 where charge q = -e or p 897 where charge q = +e!
    Last edited: Jun 15, 2007
  4. Jun 15, 2007 #3


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    The states of interest only existed in the very early universe. The physics that emerged beyond the first ~.001 second are well understood thanks to particle accelerators and observations of the universe at large.
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