The Net Advance of Physics: The Nature of Dark Matter, by Kim Griest -- Section 2D.
Next: Distribution of Dark Matter
Up: Physical Evidence
Previous: Large Scale Flows
An important ingredient in the motivation for non-baryonic dark
matter comes from big bang nucleosynthesis limits on the average
baryonic content of the Universe.
To agree with the measured
abundances of helium, deuterium, and lithium, the baryonic
content of the Universe must
be between
[13,
14, 15].
Given the large uncertainty in h this means
.
These values are far below unity, so
the theoretical predilection for
(or the
observational evidence for ) forces the bulk
of the dark matter to be non-baryonic. The lower limit of this
range is actually
above the abundance of known stars, gas, etc., and
so there also seems to be evidence for substantial baryonic dark
matter as well.
However, if one considered only the most secure dark matter, that
found in spiral galaxies, then it is completely possible that it is all
baryonic. Since this is the only dark matter which is directly
accessible to experimental detection, it is crucial to consider the
possibility of an entirely baryonic dark halo.
Next: Distribution of Dark Matter
Up: Physical Evidence
Previous: Large Scale Flows
The Baryonic Content of the Universe
BIBLIOGRAPHY