The highly successful Hot Big Bang model, first hypothesised by Gamow in the
1940s, and supported by observations of an expanding Universe and by Big Bang
nucleosynthesis, has been the standard cosmological model since the discovery
of the cosmic microwave background radiation by Penzias and Wilson in 1964.
There are, however, some crucial gaps in our understanding of the nature of the
Universe. The Hot Big Bang model does not predict perturbations in the matter
distribution of our Universe. The origin of the large scale structure, such as
planets, stars and galaxies is not known. Further, we do not know how big the
Universe is, how old, or what its main constituents are. There are a group of
early Universe models which predict primordial fluctuations in the Universe, and
using the most popular of these, ‘inflation’, the preliminary results of precision
cosmology are giving the first glimpses of values for these mysterious quantities.
The cosmic microwave background radiation gives us a ‘snapshot’ of the very
early Universe, an invaluable source of cosmological information. The Microwave
Anisotropy probe (M A P) and the Planck Surveyor satellite will provide a map of
the distribution of the cosmic microwave background over the sky, with a resolution approximately two orders of magnitude better than the previous satellite
with a similar goal, which was the Cosmic Background Explorer satellite (CO BE),
launched in the late 1980s.
The aim of this thesis is to compare and contrast the predictions of early Universe models with respect to their predictions of the distribution of the cosmic
microwave background radiation, as well as to garner information about cosmological parameters from the upcoming data. I approach this in three ways. The
first goal is to develop statistical tools to detect non-Gaussianity in the cosmic
microwave background, which would change the interpretation of the early Universe model. A significant detection of non-Gaussianity would conflict with the
predictions of the simplest inflation model. The second aim is to develop very
rapid cosmological parameter estimation methods, should inflation be supported
by the tests of Gaussianity, and the third to develop predictions for the cosmic
microwave background for the warm inflation model.