Understanding of the dark side of the universe with weak gravitational lensing

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Cosmology is the branch of astrophysics which studies the large scale structures of the Universe. It is concerned with fundamental questions about its formation, evolution and its fate. Since the discovery made by Edwin Hubble eighty years ago that the Universe is expanding, our picture of it has considerably deepened. Astronomers have now a fairly accurate idea of the physical content of the Universe, how it reached its current state, and what will its future be. However, despite the increasing number of accurate observations, and the richness of details the Big-Bang theory can now discussed among specialists, our knowledge of the Universe poses a great challenge to modern physics: more than 90 percents of matter in the Universe is not visible, it is currently attributed to a new type of matter, which physical nature remains totally unknown, and the expansion of the Universe seems to be driven by a"fluid" whose nature is also unknown. Are we on the verge of a new "Copernician" revolution? These so called "dark matter" and "dark energy" components have shaped the Universe we see today. My research focuses on the observation and the interpretation of the dark matter and dark energy distribution using a novel technique based on the gravitational lensing effect. As A. Einstein predicted eighty years ago, the light passing nearby a massive body is deflected in proportion of the mass of the deflector. Gravitational lensing can be used to measure the mass responsible for the light deflection. I am using this effect to trace, map and quantify the dark matter distribution in the Universe, which is the only way to see it "directly". The impact of this research will lead to the understanding the dark side of structure formation, i.e. from real direct observation of dark matter instead of indirect/speculations about it. Both physicists and astrophysicists have an interest in this topic: one of their challenges is to understand the nature of this new type of matter.