# Planck and GUT scales

#### arivero

Gold Member
In 1981 Dimopoulous, Raby and Wilczek, considering SUSY GUT, remark that In the ordinary theory $M \approx 10^{15} GeV$ and ... so the supersymmetric $M \approx 10^{18} GeV$. This is the same ordeor of magnitude as the Planck mass, hinting perhaps a larger unification including gravity as well

Before in 1974 Georgi, Quinn and Weinberg already were suggesting this scent: It is intriguing that we are let to contemplate elementary particle masses as high as 2 10E17 GeV, or about the same order of magnitude as the Planck mass, G^1/2=1.2206E19 GeV. Perhaps gravitation has something do to with the superstrong spontaneus symmetry breaking, or perhaps the spontaneus breakdown of the simple simple gauge group has something to do with setting the scale of the gravitational interaction.

In fact the current estimates for the SUSY GUT scale are still, I believe, at about a close factor, 1/400, of the Planck scale. It seems that any theory of quantum gravity should reflect about it. Do they?

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#### marcus

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yes the "inline tex" format "itex" makes it smaller but better placed so I can see better in one case. before you changed it, there was some overwriting.

It seems that any theory of quantum gravity should reflect about it. Do they?
I dont know of any. Or right now I cannot bring any to mind that do. maybe someone else can. I will try to remember and perhaps can dredge something up.

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#### arivero

Gold Member
(I corrected the typos, thanks Marcus)

marcus said:
I dont know of any. Or right now I cannot bring any to mind that do. maybe someone else can. I will try to remember and perhaps can dredge something up.
Of course Witten do, he somewhere presents string-based model building as an step forward in this scale-catching, even if smaller than the jump from GUT to SUSY GUT.

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#### arivero

Gold Member
marcus said:
thanks for the reference. I had never looked at this talk, given at DESY in 2002. In case anyone's interested, the abstract is here:
http://arxiv.org/abs/hep-ph/0207124
I find amusing that two of the 9 (*) papers quoting this talk are about octonions; when I was reading Witten's arguments about going up in the ladder of inclusion for GUT groups I was thinking on the resemblance with typical discussions in the newsgroups about moving forward to use quaternions and then octonions.

(*) Yep, 9 citations!!!! Between the arxived Witten papers more than one year old, it is the 6th least cited paper and the 9th least read.

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