Fundamental and beyond-standard-model physics from CMB-electron scattering

As the CMB travels through the Universe, it interacts with large-scale structure, including with the inhomogeneous electron gas that surrounds galaxies. The Compton-scattering of the CMB off these electrons leads to the Sunyaev-Zel'dovich effect. This induces new CMB anisotropies, which carry information about the distribution of electrons: their thermodynamics, density, and velocity. We can access this information with state-of-the-art high-resolution CMB surveys such as ACT and SO. I will talk about how the SZ effect in combination with a galaxy survey will constrain fundamental and beyond-standard-model physics, focusing on probes of inflation. I will also talk about more exotic CMB-electron interactions and recent constraints on beyond-standard-model particle physics, focusing on dark photon-CMB and axion-CMB interactions.