Dark Baryons
Key Concepts:
-
Second peak is observed
to be substantially lower
than first peak
-
Dark baryons of at least
the big-bang nucleosynethesis density required
Although we cannot yet claim that the second
peak is as precisely measured as the first,
we can say that (assuming it exists!) it is definitely of
lower amplitude than the first:
The current data indicate that the baryon density
is around Wbh2=0.02
This value is interesting since it is also the baryon density inferred
from the abundance of deuterium at high redshift in quasar absorption lines
and the theory of big-bang nucleosynthesis.
We now have an additional and independent
line of evidence that there are missing
baryons in the universe - i.e. that most the
baryons are not in stars. Once the second and higher peaks
are definitively measured, CMB constraints on the baryon density will sharpen
considerably (ultimately to a few percent accuracy). Needless to
say it will be interesting to see how these comparisons shape up as the
data improve.
