01 Multidisciplinary Approach
Cosmology is increasingly related to the developments in astrophysics, theoretical particle physics and gravitation. In each of these disciplines, the recent discoveries in cosmology open new challenging problems. The tools for describing the first moments of our Universe, the discovery of dark energy dominating its energy content, the distribution of dark matter in the cosmic structures, the gravitational collapse on cosmological scales, the formation of the first stars and galaxies, the nature of gravity at different scales and its relation with the other fundamental interactions and the form of space are all interrelated issues. Insights can be obtained only through a multidisciplinary approach. The cosmology team works with many national and international partners (Universities of Amsterdam, Cape Town, Columbia, Elche, Leiden, Louvain-la-Neuve, Namur, Princeton, Rome, Wisconsin ...).
02 Dark Energy and Dark Matter
Observations of the universe on large scales have shown that the visible matter represents only 5% of the total mass density in the universe and the remaining 95% are invisible to our eyes. About 25% is in the form of heavy particles which interact only through gravity, and which constitute the essential material contained in galaxies, clusters and dark matter. The remaining 75% are in the form of an exotic component with negative pressure, responsible for the accelerated expansion of the universe and filling cosmic space : dark energy. But what is the nature of dark energy and dark matter and which role do they exactly play in the formation of cosmic structures and in the fate of our Universe ...? To address these issues, LUTH’s cosmologists have suggested several hypothesis. They proposed two possible theoretical interpretations of dark energy. The first one considers that this component may be the manifestation of modified Einstein gravity on the cosmological scale. In this context the acceleration of space is the direct consequence of a distinct gravitational attraction between visible matter and dark matter. The second one interprets the recent acceleration of our Universe as an average effect of the fine structure of space and matter that would no longer be negligible contrary to what is assumed in the present standard model of cosmology. More generally, to discriminate between various cosmological models and thus different forms of dark matter and dark energy, the cosmology team at LUTH investigates the formation of cosmic structures through numerical simulations. They have realized simulations of large structures in the Universe in the presence of dark energy on high-performing supercomputers. These simulations are the most accurate in the world in terms of spatial resolution and their exploitation is part of several theoretical and observational programs.
03 Shape of space-time and early Universe.
The study of the topology of the Universe, which is not described by general relativity, early time cosmology in relation with string theory and / or quantum gravity are research themes in which the cosmology team is also very active. This work led to intense collaborations with several national and international mathematicians.