Advanced topics in modified gravity
Abstract:
These lecture series will be dedicated to different advanced topics within the framework of modified gravity theories. First of all, I will give a detailed introduction into the successful construction of General Relativity, both from a geometrical as well as field theory perspectives. Based on the assumption that General Relativity is the fundamental theory of gravity I will introduce the standard model of cosmology and discuss the tenacious challenges we are facing within this framework. Starting from the defining key properties of General Relativity I will explain the in which consistent ways these properties can be modified. Within the geometrical interpretation of gravity this will allow me to introduce more general space-time geometries and I will illustrate simpler formulations of General Relativity as well as modifications based on affine structure. In the field theory perspective I will discuss the building blocks of modifications based on additional degrees of freedom in the gravity sector. In this context I will introduce massive gravity, the Horndeski scalar-tensor theories and generalized Proca theories. If time allows, I will explain the implications of gravitational waves measurements for different modified gravity theories.