Introduction.- Linear Perturbations in Galileon Gravity Models.- The Observational Status of Galileon Gravity After Planck.- Spherical Collapse in Galileon Gravity .- N-body Simulations and Halo Modelling in Galileon Gravity Cosmologies.- Nonlinear Structure Formation in Nonlocal Gravity.- Lensing by Clusters and Voids in Modified Lensing Potentials.- Summary, Conclusions and Future Work.
Alexandre Barreira is originally from Porto, Portugal. He
completed his undergraduate Master degrees in physics in 2011 at the University
of Porto, supervised by Prof. Pedro Avelino. Barreira then carried out his PhD
at Durham University under the supervision of Prof. Carlton Baugh, Dr. Baojiu
Li and Prof. Silvia Pascoli, successfully defended his thesis in May 2015. On
the basis of outstanding overall performance during his PhD years, Barreira was
awarded the North Holland Research Physics Prize in 2012 and the Keith Nicholas
Prize in 2014 by the Department of Physics. He is now a post-doctoral
researcher at the Max Planck Institute for Astrophysics in Germany.
This unique thesis covers all aspects of
theories of gravity beyond Einstein’s General Relativity, from setting up the
equations that describe the evolution of perturbations, to determining the
best-fitting parameters using constraints like the microwave background
radiation, and ultimately to the later stages of structure formation using
state-of-the-art N-body simulations and comparing them to observations of
galaxies, clusters and other large-scale structures. This truly ground-breaking
work puts the study of modified gravity models on the same footing as the
standard model of cosmology. Since the discovery of the accelerating expansion
of the Universe, marked by the awarding of the 2011 Nobel Prize in Physics,
there has been a growing interest in understanding what drives that
acceleration. One possible explanation lies in theories of gravity beyond
Einstein’s General Relativity. This thesis addresses all aspects of the problem,
an approach that is crucial to avoiding potentially catastrophic biases in the
interpretation of upcoming observational missions.