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Fakultät für Physik - Digitale Hochschulschriften der LMU - Teil 02/05 Podcast
Morphological Studies of the CMB: Non-standard Models and Foregrounds

Morphological Studies of the CMB: Non-standard Models and Foregrounds

Fakultät für Physik - Digitale Hochschulschriften der LMU - Teil 02/05 vor 20 Jahren

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Recent measurements of the Cosmic Microwave Background (CMB) have
allowed the most accurate determinations yet of the parameters of
the standard CDM model, but the data also contain intriguing
anomalies that are inconsistent with the assumptions of statistical
isotropy and Gaussianity. This work investigates possible sources
of such anomalies by studying the morphology of the CMB. An
unexpected correlation is found between the CMB anisotropies and a
temperature pattern generated in a Bianchi Type VIIh universe,
i.e., an anisotropic universe allowing a universal rotation or
vorticity. This model is found to be incompatible with other
observations of the cosmological parameters, but correcting for
such a component can serendipitously remove many of the anomalies
from the WMAP sky. This result indicates that an alternative
cosmological model producing such a morphology may be needed. A
similar cross-correlation method applied to the microwave
foregrounds studies the variation of the spectral behaviours of the
Galactic emission processes across the sky. The results shed light
on the unexpectedly low free-free emission amplitude as well as the
nature of the anomalous dust-correlated emission that dominates at
low frequencies. As a complementary method, phase statistics apply
to situations where no a priori knowledge of the spatial structure
informs the search for a non-Gaussian signal. Such statistics are
applied to compact topological models as well as to foreground
residuals, and a preliminary analysis shows that these may prove
powerful tools in the study of non-Gaussianity and anisotropy.