The results of the analysis of all four years of DMR data have
now become available. A convenient summary of all the results is
given in Bennett
et al.
(1996) [36]. On a statistical level, the results can be used to constrain
the normalisation of a power law primordial spectrum. For a given
slope
n, normalisation is usually expressed via the implied amplitude of
the quadrupole component of the power spectrum,
, as
where
T
is the mean CMB temperature. (Note that this
value need not be the same as the
actual
quadrupole component. The fit is to a whole power spectrum as
parameterised by a given
n). For an assumed value of
n
=1, (the Harrison-Zeldovich value), Bennett
et al.
quote
. The joint best fit values of
n
and
are
and
. This restriction on the value of
n
is of course of great interest in the context of inflationary
predictions that
n
=1. It is also of interest that inflation predicts
Gaussian
fluctuations, and while this is much harder to test for than
finding the amplitude and slope of the spectrum, the data are
also consistent with this prediction. Specifically, Bennett
et al.
state `statistical tests prefer Gaussian over other toy
statistical models by a factor of
'.
With the accumulation of four years of data, the individual anisotopy features within the maps on the scale of the beam size are now becoming statistically significant. Figure 11 shows the all-sky maps at each frequency taken from Bennett et al. [36]. Some of the features in these maps away from the Galactic plane are expected to be real CMB fluctuations, since the signal to noise in these regions is now about 2 sigma per 10 degree sky patch. Indeed, features which repeat well between the different frequencies are now clearly visible.
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The Cosmic Microwave Background
Aled W. Jones and Anthony N. Lasenby http://www.livingreviews.org/lrr-1998-11 © Max-Planck-Gesellschaft. ISSN 1433-8351 Problems/Comments to livrev@aei-potsdam.mpg.de |