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Propagation de la lumière dans un Univers structuré et nouvelles approches numériques en cosmologie

Abstract : The nature of the accelerated expansion of the Universe is one of the most fundamental question of today’s cosmology. Ontological, legislatives and paradigmatic approaches have been proposed in order to solve this question. However, it is critical to put additional observational constraints in order to break degeneracies. In this context, the imprint of the acceleration of the expansion on large scale structures has a key role to play. This thesis is focused on this imprint and especially on its effects on light propagation. Accordingly to the predictions of general relativity, photons trajectories are curved near clusters, superclusters and galactic filaments causing several observable phenomena : gravitational lensing, gravitational redshift, integrated Sachs-Wolfe effects, time delays … To quantify these effects, the first simulation of structure formation on the scale of the Observable Universe have been run to construct light cones around virtual observers. It allowed us to rephrase the question of numerical simulation in cosmology and to propose new approaches based on template metaprogramming and embedded languages to create codes achieving both genericity and performance. A raytracing code in the weak-field limit based on a new meshing algorithm has been implemented. Finally, the amplitude of the effects of inhomogeneities on angular diameter distance measured using geodesics integration is above one percent beyond z=l.
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Vincent Reverdy. Propagation de la lumière dans un Univers structuré et nouvelles approches numériques en cosmologie. Astrophysique [astro-ph]. Observatoire de Paris, 2014. Français. ⟨tel-02095297⟩

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