Exploring New Frontiers in the Dark or Invisible Universe

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Cosmology gives our best evidence for new physics beyond the standard model of particle physics. To explain our Universe new particles, or key changes to established theories like general relativity, are necessary. This proposal aims to explore and constrain, theoretically and experimentally, the physics of dark matter, dark energy, neutrinos, and other nearly invisible particles. Dark matter is five times more abundant than the normal atoms in the Universe but very little is known about its particle properties. We explore the phenomenology of particle dark matter by searching for models with distinct signatures in cosmology, direct detection, or accelerators. If dark matter is self-interacting, interacts with other particles, or originates via non-thermal production it modifies the evolution of cosmological perturbations in precise and calculable ways and alters the distribution of matter in the Universe. The CMB, large-scale structure, and the distribution of matter inside galaxies provide key experimental constraints on dark-matter particle physics. We will extend and generalize my 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. Using these predictions physically self-consistent simulations of dark-matter physics can be made resulting in robust constraints on the physics of dark matter. Similar techniques allows cosmology to constrain other non-standard particle interactions, including neutrinos, and we will explore the physics of such non-standard neutrino interactions. Finally, this proposal aims to work in aide of the Canadian Hydrogen Intensity Mapping Experiment (CHIME), a CFI-funded dark energy experiment designed to measure the expansion rate of the Universe at the time dark energy started to dominate expansion. This endeavor requires novel algorithms and analysis to distinguish the dark energy signal from contamination by the dominant foreground signals. We propose to continue to develop techniques to reject foreground modes and find practical and efficient ways to connect experimental observables to theoretical models of dark energy or modified gravity.