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- 970

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## Main Question or Discussion Point

Has the energy scale (or cutoff) at which the electric charge goes to infinity (the landau pole) been calculated? I sometimes hear that QED has been probed to tiny distance scales, and I was curious how far away we are until we get to distances corresponding to the Landau pole, after which we shouldn't be able to do anymore calculations.

Also I just realized that SU(2) isospin interaction is asymptotically free. I had thought only SU(3) color interaction was asymptotically free, but from the looks of the SU(2) isospin beta function (which is negative), so is SU(2) isospin. It seems strange however that whenever I look up asymptotic freedom, there is only mention of SU(3) color asymptotic freedom and no mention of SU(2) isospin.

Also I just realized that SU(2) isospin interaction is asymptotically free. I had thought only SU(3) color interaction was asymptotically free, but from the looks of the SU(2) isospin beta function (which is negative), so is SU(2) isospin. It seems strange however that whenever I look up asymptotic freedom, there is only mention of SU(3) color asymptotic freedom and no mention of SU(2) isospin.