Shining a light on structure growth with CMB secondary anisotropies

Comparing the growth of structure between redshift 1100, when the primary CMB anisotropies were imprinted, and recent times is a powerful test of the LCDM model and for constraining dark energy and neutrino masses. Recent galaxy clustering and weak gravitational lensing measurements have suggested mild tensions (the “S8 tension”) with the CMB-calibrated predicted growth on small scales. CMB secondary anisotropies, the lensing and scattering imprints of large-scale structure on the CMB, are an alternative way to probe the amplitude of structure across cosmic time. I will discuss the findings from recent measurements of these secondary anisotropies with data from Planck, ACT and SPT and the implications of these for the S8 tension.