The Physics and Cosmology of Dark Matter, Dark Energy, and the Early Universe

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Our best evidence for new physics beyond the standard model of particle physics, new fundamental particles and fields, arises from cosmological observables. This proposal aims to explore and constrain, theoretically and experimentally, the physics of dark matter, dark energy, and the early universe. ******We are confident dark matter -- 85% of all matter in the Universe -- is something other than atomic matter. Precious little is known about its particle properties and null results from the Large Hadron Collider and other experiments have severely constrained long-heralded models for dark matter like the lightest supersymmetric partner. This motivates exploring new pathways for understanding the physics of dark matter and we propose to characterize in a generic way the impact of dark matter physics on cosmological and astrophysical observables. In particular, if dark matter interacts with other particles or itself, or is produced when relativistic, cosmological perturbations are modified in precise and calculable ways. The CMB, large-scale structure, and galactic matter distributions provide key experimental constraints on dark-matter particle physics. We will extend our existing work to make precise predictions of the initial dark matter distribution in a whole class of theories that couple dark matter to relativistic particles or themselves. This allows for self-consistent simulations to be made that can be used to calculate the impact of dark-matter physics on cosmological and galactic structure formation.******Dark energy is driving the accelerated expansion of the Universe, but the physics responsible for this is unknown. A miniscule cosmological constant is in stark conflict with theoretical predictions (the cosmological constant problem) and no compelling theoretical alternatives exist. New measurements of the expansion history of the Universe may give clues to the origin of dark energy. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a CFI-funded dark energy experiment designed to measure the expansion rate of the Universe with the 21-cm line of hydrogen. CHIME is under construction and this proposal aims to develop robust methods to reject spurious foreground contamination and find efficient ways to create data products that will provide cutting edge constraints on models of dark energy physics.******Something like inflation occurred in the early universe to generate the initial curvature fluctuations observed in the cosmos. Viable models of inflation predict nearly Gaussian fluctuations and non-Gaussian corrections reveal the strength and form of field interactions. These non-Gaussian features manifest themselves in highly distinct ways in the large-scale structure of the Universe and we propose to quantify how experiments probing unprecedentedly large volumes of the Universe, like CHIME, can constrain non-Gaussian statistics and theoretical models of inflation.**