Cosmological Constraints on Dark Matter Interactions with Ordinary
  Matter
  Dark matter interactions with electrons or protons during the early Universe
leave imprints on the cosmic microwave background and the matter power
spectrum, and can be probed through cosmological and astrophysical
observations. These interactions lead to momentum and heat exchange between the
ordinary and dark matter components, which in turn results in a transfer of
pressure from the ordinary to the dark matter. We explore these interactions
using a diverse suite of data: cosmic microwave background anisotropies, baryon
acoustic oscillations, the Lyman-$\alpha$ forest, and the abundance of
Milky-Way subhalos. We derive constraints using model-independent
parameterizations of the dark matter--electron and dark matter--proton
interaction cross sections and map these constraints onto concrete dark matter
models. Our constraints are complementary to other probes of dark matter
interactions with ordinary matter, such as direct detection, big bang
nucleosynthesis, various astrophysical systems, and accelerator-based
experiments. They exclude sufficiently large cross sections for a large range
of dark matter masses, which cannot be accessed by direct-detection experiments
due to the overburden from the Earth's atmosphere or crust.
