UCLA

Amplitudes methods have been successfully applied to various physical situations. In this manuscript we present their application to two quite distinct problems: classical gravitational-wave physics and constraining gravitational theories beyond general relativity. In chapter 1 we develop two methods for simplifying a computationally intense step in amplitudes calculations, specifically the sum over the physical states of photons and gravitons. These methods, even though generic, are developed with the application of gravitational-wave physics in mind. In chapters 2 and 3 we compute novel corrections to the Newtonian gravitational potential experienced by two spinning objects. These corrections originate in general-relativity effects. In chapter 4 we obtain bounds on Wilson coefficients of four-dimensional gravitational effective field theories. By calculating explicit examples of consistent gravitational theories and extracting the corresponding Wilson coefficients, we find that they occupy tiny islands in the Wilson-coefficient space derived. In chapter 5 we extend this analysis to dimensions higher than four. We again construct explicit gravitational theories and observe that the corresponding Wilson coefficients land in similar regions.