Séminaire doctorant : Cyril Renevey :Scrutinizing the Big Bang singularity and dark energy using experiments

Among the open questions in cosmology today, the origin of our universe and the late time acceleration of its expansion are some of the most puzzling. In this presentation, I will first expose how one can use our present day and future experiments to better understand these two open questions. Starting with our origins, I will show how one can resolve the Big Bang singularity with a big bounce using either simply positive curvature and inflation, either the consequences of loop quantum gravity on cosmology. I will then discuss what are the observable effects of such bounces on the cosmic microwave background. Later on, we will move on to the question of the cosmological constant problem and see what are the alternatives to explain the accelerated expansion. We will discuss how can we test for these alternatives using gravitational wave and how one can put constraints on string theory through the swampland program using future experiments such as Euclid and the Vera Rubin observatory.