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.

Nominated as an outstanding PhD thesis by the Durham A comprehensive overview and critical analysis of gravity theories beyond general relativity Confronts the theory with both observational evidence and simulations Includes supplementary material: sn.pub/extras

Autorentext
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.

Inhalt
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 Modied Lensing Potentials.- Summary, Conclusions and Future Work.