Astrophysics and Cosmology at the University of Sussex: FEC support for Martin Kunz

My research focuses on two main themes: The statistics of the cosmic microwave background and topological defects The cosmic microwave background (CMB) is by far the most precise cosmological data set available to us. It is therefore the best place to look for faint echos that might have been left by cosmic strings, possible remnants from phase transitions in the early universe. If any are found then we could learn a great deal about the structure of physics at very high energies. Their absence, on the other hand, puts constraints on some models of inflation. There is also a possible connection to string theory, since fundamental strings might also be detectable in the CMB. So far CMB research has focused on the power spectrum of the temperature fluctuations, not least because the distribution of the fluctuations is very close to Gaussian. However, deviations from an exact Gaussian distribution, especially if they are of primordial origin, would be extremely interesting. They might be direct remnants from inflation, for example, or afford much more precise probes of cosmic strings than the power spectrum. Deviations from isotropy on the other hand could be connected with structure on very large scales, for example if the universe is not infinite but has a non-trivial topology. This year the Planck satellite will be launched which will provide a much improved data set to study these questions. The accelerated expansion of the universe The observed accelerated expansion, often attributed to a mysterious dark energy, is considered as one of biggest puzzles in modern physics. In my research I try to approach the question from two sides: On the one hand from theoretical considerations and model-building and on the other hand from observations. At the moment I am working on a phenomenological framework that will enable observers to hunt for a few well-defined functions, which describe the dark sector and will hopefully contain vital clues about its physical nature. I am also working on the design (and hopefully later on data anlysis) of dark energy projects, for example the Euclid satellite project, which is the ESA dark energy mission proposal, and WFMOS, a proposal for a large galaxy survey. Within these projects I provide theoretical motivations for the missions, and also work on survey optimisation questions and (Bayesian) data analysis techniques. The main aim here is to build the best experiment possible, which requires both understanding which measurements are best at giving us constraints on cosmological parameters, and how to build the experiment to deliver those measurements with the highest possible precision and robustness.