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Reference : UMR7164-NADOKA-006
Workplace : PARIS 13
Date of publication : Wednesday, July 29, 2020
Scientific Responsible name : Guillaume Patanchon
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 November 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
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. Several experiments, including the recent Planck satellite mission of ESA have recently measured those perturbations with high accuracy, leading to per cent precision on the determination of cosmological parameters. The next objective of the community is to measure the polarization of the CMB and in particular to detect and constrain the B-mode (negative parity) pattern on the sky, which are the imprint of primordial gravitational waves generated during the inflation period. The LiteBIRD mission has recently been proposed to the Japanese space agency (JAXA) and has been selected at the end of phase A-1. The main goal of the mission is to measure the primordial B-mode at large angular scale of the sky with an accuracy on r (the tensor-to-scalar ratio) of less than 10-3. The LiteBIRD experiment includes a contribution from Europe and the USA, and the mission has been approved for a phase A with the French space agency CNES.
The measurement of B-mode polarization is complex and requires an unprecedented control of systematic effects originating from the instrument. The study of potential systematic effects impacts the definition of the mission configuration and observation strategy. The PhD student will simulate instrumental effects and their impact of data and develop analysis techniques to mitigate eventual residual contributions. In particular, he will focus on the modelling of the have wave plate (HWP), a critical optical element of LiteBIRD. By modulating the polarization signal the HWP allows to removes many spurious effects but on the other end possible defects might induce artefacts in the data. Those studies will be performed within a large consortium including researchers in Europe and Japan.
APC, located in the centre of Paris (France), in a building of the University of Paris, is a multidisciplinary laboratory with researchers working in five main groups: cosmology, high-energy astrophysics, gravitational waves, neutrinos and theory. The candidate will join the cosmology group, which has been involved for several years in the preparation of Euclid and LSST data processing, and whose main research themes are weak lenses, galaxy clusters and the cosmological diffuse background.
Constraints and risks
Applicants for PhD appointment will hold a M.Sc. degree in physics The position requires Good oral and written communication skills to report, to present in congress and to write articles for scientific journals.
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