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The aim of cosmology is to understand the history and structure of the universe. The Big Bang model of cosmology, which posits that the universe is expanding from an initial state which was extremely hot and dense, is now well-established. The focus of current research in cosmology is now the physics of the early universe, the nature of dark matter and dark energy, and the origin of large scale structures in the universe and how they evolve.

Map of the polarization of the Diffus Cosmological Background (Credit: ESA and the Planck Collaboration)

The Cosmology group of the APC now brings together some fifteen researchers and teacher-researchers who work closely with so many technicians and engineers. They are supported by a dozen post-doctoral students and visitors and as many PhD students. Several theses are prepared each year in the group, and we regularly welcome trainees of all levels, for a week or for several months, depending on the case.

The group participates in several projects: BOSS and its successor eBOSS have as main objective to bring constraints on the properties of the black energy. For this, the spectra of millions of luminous galaxies and quasars are measured. This will allow accurate detection of acoustic oscillations of baryons, a standard distance standard. We can thus constrain the history, the geometry and the content of the Universe. Euclid is an optical and near-infrared satellite of the European Space Agency, which is due to be launched in 2020. Its objective is to characterize black energy, to test theories of structural formation in the context of cold black matter and to confront The theories of gravity modified to the new data.

The LSST (Large Synoptic Survey Telescope) is a project of telescope in Chile, intended to carry out from the 2020s a survey of the sky of the southern hemisphere (20000 square degrees) in 6 photometric bands (visible). Its scientific objectives are very broad, but as far as APC is concerned, it is also to probe the properties of black energy, the formation of structures and possible modifications to Einstein's theory of gravity.

Planck, Polarbear and QUBIC all measure the temperature and the polarization of fluctuations of the cosmic diffuse background (CMB). It is a rich source of information on the primordial universe. Planck, an ESA satellite, was launched in 2009 and, thanks to the combination of unprecedented sensitivity and angular resolution, could bring strong constraints on the parameters describing the Big Bang model. Polarbear, located in the Atacama desert in Chile, is a CMB polarimeter with a high angular resolution. He made the first detection of B-modes from gravitational lensing using CMB data only. QUBIC, also designed to measure the polarization of the CMB, is an instrument based on innovative technology, bolometric interferometry, which combines high sensitivity with precise control of systematic instrumental effects.