Quick Physics Notes

A couple of quick notes regarding physics stories that have caught my eye:

1) Like Doug Natelson, I’m surprised that there hasn’t been more discussion about the PRL claiming to have seen vacuum birefringence. The idea here is that a group in Italy passed light through a huge rotating magnetic field (5 Tesla, or about 100,000 times the Earth’s magnetic field), and found that the polarization of the light was rotated by a tiny amount. The effect is, I gather, larger than expected, which might be explained as the result of interactions between their laser photons, photons from the magnetic field, and some unknown low-mass particle.

I haven’t said much about it because I don’t really understand the physics of the interaction well enough to comment sensibly. I’m surprised, though, that I haven’t seen it discussed on any of the many blogs by people who do understand this stuff. Healthy skepticism, or an unhealthy fixation on big accelerators as the only tests of particle physics? Or is it off the radar because it appeared in an obsolete print journal?

(I downloaded the paper, but haven’t had time to look closely at it. I think it’d be really cool if it holds up, and the “if” is not quite as big as for the gravitomagnetism stuff, but still pretty big. I’ll take a closer look in my copious free time, maybe.)

2) Not really an exciting physics development, but Gordon Watts mentions a job talk by a guy I know from MIT. This is interesting primarily because of the cool picture of their optical table. Look at all those mirrors!

Makes me nostalgic for BEC work, it does…

3) If you just can’t get enough of abstract arguments about multiverse theories, World Science provides your daily fix.


  1. #1 Jeff
    March 30, 2006

    Re: #2. I was rather surprised that he blogged about a job search candidate by name, especially if the job search is still going on. It seems to not be the best professional choice to me.

  2. #2 Chad Orzel
    March 30, 2006

    Now that you mention it, that is kind of weird.

  3. #3 Sean Carroll
    March 30, 2006

    I hope to blog briefly about the birefringence stuff at some point. If it’s right, the most straightforward new-physics explanation is a new axion-like kind of particle. Problem is, the new particle is in deep conflict with all sorts of astrophysical bounds. But my friends tell me the experimenters are respectable, so it’s worth keeping an eye on.

  4. #4 Alejandro Rivero
    March 30, 2006

    Besides print, it is also online


  5. #5 Alejandro Rivero
    March 30, 2006

    And http://arxiv.org/abs/hep-ex/0512022

    I was also surprised after reading Doug Natelson note, so I took a look to the paper and it is disturbing, on one side it seems it just gets to land in a casually empty zone of parameter space, it puts a mass limit in the misterious scale of 10^-3 eV where everybody sees things nowadays, and it order to land there it neds some mass at 1000 TeV… kind of oasis in the desert?

  6. #6 Chad Orzel
    March 30, 2006

    I should probably note that the specific reasons suggested for the lack of discussion were intended as a joke…

    I think it’s reasonable to be somewht skeptical at this point– the Fourier spectrum they show in the paper looks very nice, but the scatter plots they show later on are less convincing.

  7. #7 Alejandro Rivero
    March 30, 2006

    Joke is understood :-). I was pointing to the electronic version because it adds to the surprise that the citebase evolution of the preprint has been slow during the half-year it has been there arxived.

  8. #8 Uncle Al
    March 30, 2006


    The researchers “successfully” used supercon lead or niobium to observe the “effect” with a piddling 3:1 signal:noise ratio. Both those supercons have critical temperatures below 10 K and critical magnetic fields at 4 K temp of less than a kilooersted. Crappy set of experiments given the outrageous claims. It should be repeated at 4 K using annealed Nb3Sn or the like with a critical temp around 18 K and a critical field more than 200 times larger.

    High quality robust niobium bronze supercons are not overmuch difficult to fabricate. Surface-metallized stable cores (fused silica, stabilized cubic zirconia or toughened zirconia, sintered or single crystal alumina) ditto. Extraordinary claims should not be based upon marginal foundations. Substantially superior materials and larger angular velocities are attainable without exceptional incremental efforts. Get the noise down and the signal up (or gone).

    Supercon solenoid solar axion telescopes are clean nulls,


    and much more believable experiments resident in the contested neighborhood.

  9. #9 NL
    March 30, 2006

    It’s really frustrating that I completely missed that article because it appears to have not shown up in the PRL RSS feed. Or at least Bloglines says it didn’t.

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