On the origin, dynamics, and detection of superheavy, ultralight, and composite dark matter.
In this thesis we explore numerous theoretical and phenomenological ideas in the quest to uncover the nature and workings of dark matter in the universe. In Chapter 1 we provide a broad introduction to the thesis, introducing many theoretical concepts that will be useful for later chapters. In Chapter 2 we describe how gravitational fields, specifically those of expanding universes, can lead to the production of particles. This is identified as a mechanism through which dark matter could have been created in the early universe. In Chapter 3 we explore mechanisms for making very heavy dark matter particles. We identify gravitational wave signatures of such dark matter candidates and motivate gravitational wave detectors as tools for uncovering the fundamental nature of dark matter. In Chapter 4 we describe how gas clouds located near the center of the Milky Way can act as very sensitive probes of many dark matter candidates, namely milli-charged, dark photon, vector portal, and composite dark matter models. These clouds complement existing terrestrial experiments for dark matter. In Chapter 5 we show that plastic track detectors mounted on the Skylab space station and underground in the Ohya stone quarry in Japan can help place new constraints on Strongly Interacting Massive Particle models of dark matter. Our work revisits old constraints on such dark matter models and, through a more careful treatment, places stronger constraints on them.