Following up on Paul's posting of ~ 2 weeks ago:
The paper by Nodland & Ralston is now in print, Phys. Rev.
Lett.78.16, 21 April 1997, pp.3043-3046.
They suggest that the directional effect in the polarization of
synchrotron radiation from distant galaxies is due to an interaction of
the electromagnetic field with another vector field which defines an
apparently preferred spatial direction. The 1st thing I thought of was
somewhat different, an effect due to cosmic rotation, as in the Goedel
universe. In fact, EM radiation in such cosmological models has been
investigated (e.g., R. X. Saibatalov, Gen. Rel. & Grav. _27_, 1995,
697), but what you get there is like the effect in a doubly refracting
crystal, with rays being split in 2. So this doesn't seem to work.
OTOH, just introducing a new field seems pretty ad hoc.
George L. Murphy
gmurphy@imperium.net
http://www.imperium.net/~gmurphy