I’m currently revising the book chapter based on the original “Bunnies Made of Cheese” post, which deals with virtual particles and Quantum Electro-Dynamics. The best proof of the power of QED is the measurement of the anomalous magnetic moment of the electron, where experiment and theory agree to something like thirteen decimal places.

In double-checking things this morning, I find that the Gabrielse group has released yet another improved measurement of the electron g-factor since the last draft of this chapter. I’ve updated the current draft accordingly, and continue to be amazed by the whole field. The bastards will probably push it out another decimal place or two before the book sees print, too.

Interestingly, the analogous quantitiy for the muon seems to show a small discrepancy between the experimental and theoretical values, with the theoretical value being slightly larger than the experimental (2.00116592287 vs. 2.00116592080, if I’m reading this preprint correctly). It’s not entirely clear to me whether this is a possible sign of new physics (as a 3.3-sigma effect, it’s not that definitive), or just a sign that the calculations and experiments are really tricky.

Anybody with relevant knowledge of the muon situation, please leave me a comment. Otherwise, I’m moderately likely to say something silly when I try to add this to the book.


  1. #1 onymous
    July 10, 2008

    Muon g-2 is a tricky issue. It seems to be taken most seriously by people who really want TeV-scale supersymmetry to be true. There are a lot of 2 and 3 and 3.5 sigma effects floating around in the world, though, and some are universally ignored while others aren’t. Maybe the LHC will discover supersymmetry and in hindsight muon g-2 will be important. Maybe not.

  2. #2 cecil kirksey
    July 13, 2008

    In a reply to “bunnies made of cheese”:

    Shalev: What’s confusing is that, given that these virtual particle pairs appear randomluy, wouldn’t it work out to about 50% of the time where the positive particle enters the black hole and the anti-particle escapes? That is, wouldn’t it work out that the mass of a black hole remains constant?

    Chad: The mistake you’re making is in assuming that anti-particles have negative mass. In fact, both particles and anti-particles have positive mass, so whichever one escapes being eaten by the black hole increases the total mass of the larger universe. That mass increase has to come from somewhere, because energy needs to be conserved on longer time scales, and the mass of the black hole is reduced as a result.

    This confuses me. Suppose the virtual particles are photons. Now a real photon has real energy and a real relativistic mass, correct? The virtual particle has the same charteristics except…?? Would it be negative energy? Thus decreasing the mass of the black hole? But again why do only real particles appear in the radiation? But maybe this is just a definition. But then if the particle pair was an electron/positron pair where does the mass reduction come from?

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