From: Robert A. Knop Jr. (robert.a.knop@vanderbilt.edu)
Date: Sun May 04 2003 - 07:14:37 PDT
I don't know a whole lot about this topic, but here's a thought. Does
anybody know what the limits from the CMB on these oscillations are?
My simplistic thought on this:
* The CMB is optically thick and a blackbody, thus we should know the
flux emitted by it.
* We know the angular diameter distance to the CMB, thus we know the
luminosity distance to the CMB.
* Therefore, we should be able to use flux measurements of the CMB to
set limits on photons oscillating away into other strange things.
Are there holes in this? E.g., would photon/axion oscillations also
throw off our distance measurement? (I can't see how that would change
the angular diameter distance.) How well calibrated is the absolute
flux of the CMB? Enough to do anything useful with this?
Given that the CMB is as far back as we can see photons at all, if we
can use it as a "standard candle", given good flux measurements it
should be able to provide the best possible limit on this. The only
problem is that I don't really have a good idea about how well one can
calibrate the absolute flux measurement.
-Rob
-- --Prof. Robert Knop Department of Physics & Astronomy, Vanderbilt University robert.a.knop@vanderbilt.edu
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