Is the Universe Birefringent?

This page contains links to various papers having to do with the interesting question of whether light propagates isotropically through the Universe.

Borge Nodland and John Ralston claimed in Physical Review Letters (78, 3043, 1997) to have detected rotation in the polarization of radio waves from distant galaxies, as if the Universe were birefringent (sort of, but not really, like a giant piece of icelandic spar). Daniel Eisenstein and I published a brief comment explaining an error in this paper. We concluded that there is at this point no demonstrated evidence that this effect is real.

Our comment, which was published in Physical Review Letters (vol. 79, p. 1957), is available from this site in either HTML or PostScript format. The PostScript format will look nicer and be easier to read; the HTML is provided for those whose Web browsers don't know how to handle PostScript.

If you really don't like the HTML version, but your machine won't let you view the PostScript, you can always download a free PostScript previewer. If you have trouble getting these files, or if you want more information, send me e-mail.

Here are some related sources of information:

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