A non-linear solution to the S8 tension - II. Analysis of DES Year 3 cosmic shear

Weak galaxy lensing surveys have consistently reported low values of the S-8 parameter compared to the Planck lambda cold dark matter (Lambda CDM) cosmology. Amon & Efstathiou used KiDS-1000 cosmic shear measurements to propose that this tension can be reconciled if the matter fluctuation spectrum is suppressed more strongly on non-linear scales than assumed in state-of-the-art hydrodynamical simulations. In this paper, we investigate cosmic shear data from the Dark Energy Survey (DES) Year 3. The non-linear suppression of the matter power spectrum required to resolve the S-8 tension between DES and the Planck Lambda CDM model is not as strong as inferred using KiDS data, but is still more extreme than predictions from recent numerical simulations. An alternative possibility is that non-standard dark matter contributes to the required suppression. We investigate the redshift and scale dependence of the suppression of the matter power spectrum. If our proposed explanation of the S-8 tension is correct, the required suppression must extend into the mildly non-linear regime to wavenumbers K similar to 0.2 Mpc(-1). In addition, all measures of S-8 using linear scales should agree with the Planck Lambda CDM cosmology, an expectation that will be testable to high precision in the near future.