报告人简介：
        Dr. Yannick Mellier is an astronomer at the Institut d'Astrophysique de Paris.
He is leading the "Gravitational Lensing and Cosmology" group and is the Director
of the Terapix Data Center. He co-discovered the giant gravitational arc in 1987
and got the first confirmation that it was a gravitational lensing effect in
1988 by measuring the first redshift of an arc (punching a "curved slit").  He
then moved to a very new field in 1993, the weak gravitational lensing, that
are the very faint distortion on galaxies produced by dark matter. In 1999 he
detected for the  first time, with Ludovic van Waerbeke, the gravitational
lensing effect produced by the large-scale structure of the Universe (the Cosmic
Shear). Over the last 7 years, Yannick Mellier co-led the Canada-France-Hawaii
Legacy Survey (500 nights with the world largest CCD Camera Megacam on the 3.6m
telescope Canada-France-Hawaii telescope). This survey produced the best results
ever obtained, so far, on cosmic shear. Yannick Mellier got the Ricard's Prize of the
French Physical Society in 2006 and the French Centre National de la Recherche
Scientifique (CNRS) CNRS-Silver Medal in 2009 for the discovery and his results on cosmic shear.
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报告摘要：         
        Weak gravitational lensing by cosmic structures of the universe produces
coherent shear fields that can be directly observed from the ellipticity of
lensed galaxies. The statistical analysis of the shapes of lensed galaxies then
reveals, almost directly, the properties of the projected (dark) matter power
spectrum.  Weak lensing can then be used to challenge theoretical models against
the observed (dark) matter power spectrum. One of its most promising goal is the
exploration of dark energy or of alternative theory of gravitation that could
supersede General Relativity. In this review, I will discuss what we learned from
the Canada-France-Hawaii Telescope Legacy Survey and other weak lensing surveys,
like COSMOS, about dark matter, dark energy, neutrinos and some modified gravity
models.  I will also discuss future prospects for the next generation surveys.