2016/10/12 by Sandrine Schlögel, Schlögel, Sandrine
Physics and Astronomy · #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #Noncommutative and Quantum Gravity Theories #Relativity and Gravitational Theory #astro-ph.CO #gr-qc
paper · pdf · doi:10.48550/arxiv.1610.03622
Ph.D. thesis, October 2016, 211 pages
arxiv created 2016/10/12 · openalex publication_date 2016/10/12 · arxiv updated 2016/10/13 · openalex created_date 2016/10/21 · openalex updated_date 2026/07/28
Modifications of gravity have been considered to model the primordial inflation and the late-time cosmic acceleration. Provided that modified gravity models do not suffer from theoretical instabilities, they must be confronted with observations, not only at the cosmological scales, but also with the local tests of gravity, in the lab and in the Solar System, as well as at the astrophysical scales. Considering in particular sub-classes of the Horndeski gravity, we study their observational predictions at different scales. In order to pass the local tests of gravity while allowing for long-range interactions in cosmology, Horndeski gravity exhibits screening mechanisms, among them the chameleon. The chameleon screening mechanism has been tested recently using atom interferometry in a vacuum chamber. Numerical simulations are provided in this thesis in order to refine the analytical predictions. At the astrophysical scale, Horndeski gravity predicts a variation of the gravitational coupling inside compact stars. Focusing on Higgs inflation, we discuss to what extent the Higgs vacuum expectation value varies inside stars and conclude whether the effect is detectable in gravitational and nuclear physics. Finally, the covariant Galileon model exhibits non-linearities in the scalar field kinetic term such that it might pass the local tests of gravity thanks to the Vainshtein screening mechanism. We discuss if a sub-class of the covariant Galileon theory dubbed the Fab Four model leads to a viable inflationary phase and provide combined analysis with neutron stars and Solar System observables.