Cosmologie

Caractérisation et commissioning de l’instrument QUBIC dédié à l’observation de la polarisation du rayonnement fossile

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.  Dans cette perspective, l’expérience internationale QUBIC (Q and U Bolometric Interferometer for Cosmology) utilise une méthode de détection innovante basée sur l’interférométrie bolométrique. Celle-ci permet de combiner l’immunité aux effets systématiques induit par l’interférométrie et la sensibilité des détecteurs cryogéniques incohérents.

Characterization and commissioning of the QUBIC instrument dedicated to the measurement of the Cosmic Microwave Background polarisation

The characterization of the polarized fluctuations of the Cosmic Microwave Background (CMB) is a major scientific way to further understand the primordial Universe. QUBIC (Q & U Bolometric Interferometer for Cosmology) is an international experiment dedicated in the measurement of this signal. It is based on a new detection technique called bolometric interferometry in order to combine the high immunity to systematic effects of an interferometer with the high sensitivity of low temperature incoherent detectors.

Multichroic detectors for Cosmic Microwave Background polarisation observation

To optimise the optical performances of a future space instrument dedicated to CMB polarisation observations, it will be very interesting to reduce the physical size of the focal plane without decreasing the number of detectors. An elegant way to reach such architecture would be to use multichroic detectors that are sensitive to multiple frequency bands. A large bandwidth antenna could be used to feed multiple detectors (TESs or KIDs) through different bandpass filters.

Inflationary non-Gaussianities

Inflation is an important theory of the primordial universe that explains amongst other things the origin of the fluctuations observed in the cosmic microwave background (CMB) and of the large-scale structure of galaxy clusters. However, there are many different inflation models and one of the challenges of modern cosmology is to find ways to distinguish these models at the level of their predictions for observables, in order to confront them with experimental data.

Evaluation of the impact of systematic effect on the future LiteBIRD satellite mission for the measurement of the Cosmic Microwave Background B-mode polarization

The Cosmic Microwave Background (CMB) radiation is a relic emission from 380 000 years after the Big-Bang. The small temperature fluctuations, resulting from quantum perturbation generated in the early Universe, contain precious information about the physics of the primordial Universe and the cosmological parameters describing in the framework of the standard cosmological model, the dynamics of the Universe and its physical content.

Deep Learning to Find Clusters

The goal of this thesis is to apply deep learning to the detection of galaxy clusters in astronomical surveys.  Clusters are the most massive objects in the universe, hosting hundreds of galaxies and a gaseous intra-cluster medium (ICM) at temperatures of tens of millions of Kelvin.  They are detected as galaxy over-densities in optical/near-infrared (NIR) imaging, through the X-ray emission of their ICM or via the Sunyaev-Zeldovich (SZ) effect, a distortion of the cosmic microwave background spectrum generated by photon-electron scattering in the ICM.  Clusters serve as powerful probes of

Quest for primordial gravitational waves: advanced map-making for the next generation of CMB B-mode polarization data sets.

Many popular theories of the early Universe predict that gravitational waves were generated in the very first moments of its life. These theories generally invoke new physics from beyond the standard model of the particle physics and the primordial gravitational waves are believed to carry clues about the nature of those new physics laws. Detecting the primordial gravitational waves would thus have revolutionary impact on our understanding of cosmology and fundamental physics.

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