Abstract

Percent level measurements of the kSZ effect (due to bulk motion of free electrons) will be possible with upcoming CMB and galaxy surveys, so it is timely to ask what science can be extracted with such measurements. I will discuss how recasting kSZ tomography as a bispectrum measurement allows for a unified framework under which the “galaxy optical depth degeneracy” problem becomes clear; the cosmic velocity field and an astrophysical power spectrum involving the electron density appear together. However, these are degenerate only up to an overall amplitude. I discuss how scale-dependent effects like those due to primordial non-Gaussianity or dark energy perturbations can be constrained with kSZ (with factors of >2x improvement on fNL possible with future surveys). I will also discuss a way to break the optical depth degeneracy using the dispersion measures of fast radio bursts (FRBs) allowing for strong constraints on sigma8. Finally, I discuss calibration of baryonic feedback in weak lensing measurements using kSZ measurements of the electron density profile.