Studying the early universe with non-gaussianities

According to most theories, the universe originated approximately 13 billion years ago in the so-called Big Bang. The details of the physical processes occurring in the first fractions of a second during the birth of the universe are still to be cleared. The early universe, containing dense hot gas and radiation, was, after expanding for about 300 000 years, cold enough for the first atoms to form. After this process, radiation was allowed to stream freely without being scattered on charged particles. Thi s radiation has survived to the present time and is called the cosmic microwave background (CMB). Because the universe has cooled further, this radiation can now be observed as microwaves. The CMB was discovered in 1965 and since then it has been the tar get for a large number of ground based, balloon and space borne experiments. In 1992, the COBE satellite discovered small fluctuations in the intensity of the radiation, being relics of the density fluctuations in the early universe. These have now been o bserved in great detail over the full sky by the WMAP satellite and data with even higher resolution will be taken with the upcoming Planck satellite. As these fluctuations reflect the density fluctuations in the universe a short time after the Big Bang , they also contain a wealth of information about the physical processes which created these fluctuations. By applying statistical analysis methods to these fluctuations, several parameters describing the present universe as well as its evolution can be i nferred. Most of these analyses are carried out assuming that the statistical distribution of the fluctuations are gaussian. The distribution is however expected to be slightly different from gaussian, and by studying the details of this non-gaussianity, crucial information about the physical processes taking place in the early universe can be extracted. This project aims at developing efficient methods to obtain such information.