Sonder l’énergie noire avec les neutrons

There is a deep connection between cosmology - the science of the infinitely large - andparticle physics - the science of the infinitely small. This connection is particularlymanifest in neutron particle physics. Basic properties of the neutron { its ElectricDipole Moment and its lifetime { are intertwined with baryogenesis and nucleosynthesisin the early Universe. I will cover this topic in the first part, that will also serve as anintroduction (or rather a quick recap) of neutron physics and Big Bang cosmology. Then,the rest of the manuscript will be devoted to a new idea: using neutrons to probe modelsof Dark Energy. In the second part, I will present the chameleon theory: a light scalarfield accounting for the late accelerated expansion of the Universe, which interacts withmatter in such a way that it does not mediate a fifth force between macroscopic bodies.However, neutrons can alleviate the chameleon mechanism and reveal the presence of thescalar field with properly designed experiments. In the third part, I will describe a recentexperiment performed with a neutron interferometer at the Institut Laue Langevin thatsets already interesting constraints on the chameleon theory. Last, the chameleon fieldcan be probed by measuring the quantum states of neutrons bouncing over a mirror. Inthe fourth part I will present the status and prospects of the GRANIT experiment atthe ILL