Probing Dark Energy Models with Neutrons
Sonder l’énergie noire avec les neutrons
Résumé
There is a deep connection between cosmology - the science of the infinitely large - and
particle physics - the science of the infinitely small. This connection is particularly
manifest in neutron particle physics. Basic properties of the neutron { its Electric
Dipole Moment and its lifetime { are intertwined with baryogenesis and nucleosynthesis
in the early Universe. I will cover this topic in the first part, that will also serve as an
introduction (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 models
of Dark Energy. In the second part, I will present the chameleon theory: a light scalar
field accounting for the late accelerated expansion of the Universe, which interacts with
matter 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 the
scalar field with properly designed experiments. In the third part, I will describe a recent
experiment performed with a neutron interferometer at the Institut Laue Langevin that
sets already interesting constraints on the chameleon theory. Last, the chameleon field
can be probed by measuring the quantum states of neutrons bouncing over a mirror. In
the fourth part I will present the status and prospects of the GRANIT experiment at
the ILL.
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