Of course, there are a number of areas in which cosmological theory
and observations are not in obvious agreement. The space available
does not permit an exhaustive review, so I will concentrate on the
following topics which seem to me to be the most important: big bang
nucleosynthesis, galaxy centers, dark matter substructure, and angular
momentum. Fortunately, some areas which had seemed problematic now
seem less so. For example, the low values of the quadrupole and
octopole CMB anisotropies reported by WMAP are revised upward in an
improved analysis, and are now in good agreement with the
CDM
predictions [14].
And the possibility that the first year WMAP
data imply that the visible universe might be topologically complex
and smaller than the horizon
[15]
has now been stringently constrained
by the absence of pairs of circles in the WMAP data
[16].
Another topic that has received more attention in the press than is
warranted
by the science is the discovery of massive galaxies at high redshifts
[17].
Although these observations challenge some overly simplified
theories of galaxy formation
[18],
there are plenty of sufficiently
massive halos at the relevant redshifts (with
8 = 0.9) to host
the galaxies in question, as Figure 1 shows.
 |
Figure 1 Curves show the cumulative number
density of dark matter
halos more massive than 1011 to 1015
M |
(from
top to bottom, as labeled), as a function of redshift, calculated using
an improved Press-Schechter formula
[