  The small-scale cosmic microwave background (CMB) is dominated by
anisotropies from the kinematic Sunyaev-Zeldovich (kSZ) effect, and upcoming
experiments will measure it very precisely, but the optical depth degeneracy
limits the cosmological information that can be extracted. At the same time,
fast radio bursts (FRBs) are an exciting new frontier for astrophysics, but
their usefulness as cosmological probes is currently unclear. We show that FRBs
are uniquely suited for breaking the kSZ optical depth degeneracy. This opens
up new possibilities for constraining cosmology with the kSZ effect, and new
cosmological applications for FRBs.
