Visiting Researchers in Theoretical Cosmology

We aim to bring leading researchers in theoretical cosmology to Portsmouth in order to: (a) build new collaborations and exploit existing collaborations; (b) enhance the quality and impact of our existing research programme in theoretical cosmology; (c) share visitors' research expertise with staff, post-doctoral researchers and students. Our research is based on a theoretical understanding of the physics and gravity at work in the Universe, from the very high energies in the early Universe, to the low-energy late Universe. We will use this understanding to develop ways of confronting theoretical models with the growing amount of data from massive cosmological surveys. These surveys include ones in which Portsmouth is directly involved (e.g. SDSS2+3 and DES). Our research focuses on 3 main areas: (1) Primordial cosmological perturbations: Small fluctuations that are generated in the very early universe by quantum processes provide the seeds for the growth of galaxies and clusters of galaxies. The properties of these fluctuations leave subtle imprints on the radiation and the large-scale structure in the Universe. These imprints need to be computed and then compared with observational data. (2) Brane-world models of inflation and dark energy: Brane-world models are motivated by string theory, and describe the observable Universe as a 4-dimensional brane embedded in a higher-dimensional spacetime. Typically they modify the standard model at high energies, with interesting implications for primordial perturbations. Some models can also be used to understand the late-time acceleration of the Universe, which is attributed to Dark Energy in the standard model. (3) Probing the Dark Energy or Modified Gravity: The acceleration of our Universe today presents one of the greatest challenges to theoretcial cosmology. It is due to either a dark energy field, or a modification of General Relativity on large scales. The evolution of structure in the Universe provides a means of distinguishing between different models of dark energy or modified gravity. Theoretical predictions need to be compared with observational data. In particular, the data allows us in principle to test whether or not General Relativity breaks down on large scales.