Yet Another One Down!

It looks like one more of my favorite crackpot notions has bit the dust. It's known theoretically (no experimental evidence) that a uniformly accererated observer should experience a particle flux called Unruh radiation. The acceleration necessary to make this observable is beyond ordinary capabilities, but I had been interested in the effect for electrons in atoms, nucleons in the nucleus, quarks in a nucleon, etc. It seems that notion is vain, since according to Emil T.Akhmedov, Valeria Akhmedova, and Douglas Singleton there is No Unruh-like Radiation for circular motion (hep-th/0607026).

By studying the response function for a detector in uniform circular motion we show that no Unruh-like radiation will be detected. Thus, it is not possible to measure the Unruh effect using circularly moving electrons in a particle accelerator.

The motions I mentioned are not uniformly circular, but it looks like the result is probably more general.

For a detector in uniform circular motion we found that its transition rate is essentially that of a detector in uniform linear motion, indicating that a detector in circular motion should not see any Unruh-like radiation. It is therefore not possible to observe the effects of Unruh-like radiation on the polarization of electrons in storage rings as claimed in [2].

This agrees with the tunneling calculation for circular motion [3]. In the case of the tunneling picture the physical reason for the lack of Unruh radiation was the lack of a horizon or barrier which would prevent some photons from reaching the detector. For linear acceleration, a, photons some distance behind the observer will not reach the observer. For circular motion nothing prevents any photon from eventually reaching the circularly moving observer.

Oh well.