A universe of dark sectors

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Our Universe appears to be filled with matter that is relatively inert and that cannot be explained within the existing Standard Model (SM) of particle physics. This non--luminous matter has been detected through its gravitational influence in a wide variety of astrophysical environments. The broad agreement between gravitational probes has inspired a concerted multi-disciplinary effort to characterize the microphysical nature of this dark matter (DM). Inspired by the rich structure of the SM, where there are many elementary particles and interactions that can form myriad composite states, the DM may be part of a sector that is complex and contains auxiliary forces and matter fields. Any observationally viable dark sector must be very decoupled from the SM since all efforts to detect DM via non--gravitational interactions have thus far yielded null results. Additionally, the space of possible dark sector theories is incredibly vast. A systematic study of dark sectors may therefore seem a daunting task. However, in this proposal I will outline concrete ways to make progress in the next five years with an emphasis on synthesizing information from a variety of astrophysical and condensed matter systems. By testing DM over the wide range of lengthscales, timescales, and ambient environments spanned by these systems, my research group will interrogate a multitude of theoretical possibilities for what the DM is made of and how it interacts. In particular, the primary objectives I outline in this proposal involve testing dark sectors where i) DM is comprised of a mix of non-degenerate states that can scatter inelastically through a dark force and alter structure formation, ii) where DM annihilation or decay injects energy into the intergalactic medium, iii) where strong dynamics beyond the SM creates primordial black holes as a substantial fraction of the dark matter, and iv) where there are light dark sector degrees of freedom with enhanced coupling to SM particles in dense environments (including stellar interiors and laboratory-based condensed matter systems) due to in-medium effects. In carrying out this research program, my group will advance the quest to understand the nature of DM as a basic building block of our Universe. Along the way, group members will develop the necessary skills to become leaders in particle physics and beyond.