L’étude des fluctuations polarisées du rayonnement fossile à 3K (Cosmic Microwave Background, CMB) apparaît aujourd’hui comme une voie incontournable pour progresser dans notre compréhension de l’Univers. Le niveau de signal attendu, quelques nK pour le mode B le plus faible, requiert une chaîne de détection à la fois ultra sensible et extrêmement immune aux effets parasites instrumentaux.

The quest for B-mode polarization of the Cosmic Microwave Background is among the most promising topics in Observational Cosmology as it would open a window on the inflation era. It also one the most challenging as the expected is very small and require high sensitivity and low systematic instruments with wide frequency coverage in order to separate the primordial signal from foreground emissions.

The primary objective of cosmological research in the coming decade is to understand the accelerated expansion of the Universe, attributed to either a dark energy component or a modification to gravity on cosmic scales.  ESA’s Euclid mission is dedicated to probing the physical origin of the acceleration through measures of large-scale structure.  Galaxy clustering, gravitational lensing and galaxy cluster abundance are the three central observational probes. 

CMB B-mode studies are amongst the most exciting, contemporary endeavors in the field of cosmology. They are broadly expected to provide a new, unique window on the physics of the very early Universe, giving a very strong evidence in favor of inflation as a correct paradigm, within which to model this phase of the Universe's evolution, but also potentially constraining some of the fundamental energy scales of physics. These are hoped to provide some essential clues for high energy physics models.

CMB B-mode studies are amongst some of the most exciting, contemporary endeavors in the field of cosmology. They are broadly expected to provide a new, unique window on the physics of the very early Universe, potentially detecting primordial gravitational waves, giving a very strong evidence in favor of inflation as a correct paradigm, within which to model this phase of the Universe's evolution, and thus potentially constraining some of the fundamental energy scales of physics. These are hoped to provide some essential clues for high energy physics models.

Radio astronomy is undergoing a period of rapid advances because of digital techniques that allow an improvement in sensitivity of several orders of magnitude. The universe nearby and the initial conditions of the universe have now been characterized at great precision thanks to modern galaxy surveys and precision measurements of the cosmic microwave background. But the intermediate epoch, sometimes dubbed the “Dark Ages,” remains largely unexplored. However precision measurements using the 21cm line will allow a detailed three-dimensional characterization of this intermediate epoch.

Radio astronomy is undergoing a period of rapid advances because of digital techniques that allow an improvement in sensitivity of several orders of magnitude. The universe nearby and the initial conditions of the universe have now been characterized at great precision thanks to modern galaxy surveys and precision measurements of the cosmic microwave background. But the intermediate epoch, sometimes dubbed the “Dark Ages,” remains largely unexplored. However precision measurements using the 21cm line will allow a detailed three-dimensional characterization of this intermediate epoch.

Spider is a balloon-borne experiment designed and flown to study the cosmic microwave background. More information about Spider can be found at http://www.princeton.edu/jones/research/spider/.

Courant 2015, la collaboration Planck a publié les résultats de la mesure du spectre de puissance angulaire des anisotropies du CMB en température et polarisation, permettant de contraindre avec une précision sans précédent les six principaux paramètres nécessaires pour expliquer les données.

Analysis and modelling of polarized sky emission in WMAP and Planck data sets

In 2015, the Planck collaboration has published the results of the measurement of the temperature and polarisation angular power spectra of CMB anisotropies, constraining with unprecedented accuracy the six major cosmological parameters necessary to fit the data.