Combining theory and observations - a sample study of the interplay between cosmology and particle physics

To my teacher Mr. Kedar Soni, who introduced me to the awesomeness of physics! i Acknowledgements Today, I take one more step towards my dream of being a physicist, I pause for a while and look back to see the smiling faces of many who helped me. By blaming all of them who are responsible for me to be here, I wish to express my gratitude and happiness for the fact that they are there. The biggest component of life is always the parents. (As long as you are single!) I thank Aai, Baba and Prachi for letting me escape home and live life of a self-imposed exile. I shall continue to do so. I thank Manuel, who has been both my boss and a friend. Without him, I would not have dared to divulge in such diverse topics. Manuel, thanks for giving me the confidence that I am capable of doing so. I will invariably miss the lunch and coffee table discussions. Without them, I would not have understood the Large Scale Structure of the Earth, from history and geography to politics and economics. I also thank you for giving me the opportunity of numerous tours around the world. You fulfilled one of the basic reasons for why I came to research. I dearly wish, we continue to work together. I also thank Herbi, my second mentor who always helped me in more than one way. I take this opportunity to thank Cristiano and Prof. Klaus Desch for being my examiners. I also thank UniverseNET for the always happening research environment. Satisfying the quench of independent research is never possible without awesome collaborators. From my first collaborator Prof. Mitsuru Kakizaki until my current gang, I thank all for numerous good evenings, free dinners and fantastic physics discussions. I especially thank Oscar and Renata for my superb time in Brazil, I am sure I will continue to visit you. Above all, life is empty without friends, without whose encouragement and constant support I would have never come so far. Thank you Suyog, Sandesh, Pawan and Neha for mailing me from time to time asking whether am alive or dead. I am proud to have you in my life. Anyone, who has left his/her country to come into a culture completely unknown would know the excitement and fear of facing it. Bonds and relationships are formed over a period of time …