I wish to thank my supervisor ThomasÅgotnes for his support and guidance throughout writing this thesis. ThomasÅgotnes allowed me to work independently and still provided interesting ideas and excellent feedback, especially in the last hectic weeks. He also initially introduced me to the problem, which made this thesis possible. I would also like to thank Marija Slavkovik and Truls André Pedersen for many useful discussions surrounding the problem.I will never be able to thank my family enough for their endless support and motivation throughout the writing of the thesis, especially my mother who provided words of encouragement almost every day in the last weeks. Finally, I would like to thank Neil Anders for support and many useful discussions, not just throughout my thesis but throughout both my bachelor's and master's degree.