Abstract
In order to investigate the origin of the ongoing tension between the
amplitude of matter fluctuations measured by weak lensing experiments at low
redshifts and the value inferred from the cosmic microwave background
anisotropies, we reconstruct the evolution of this amplitude from $z\sim2$
using existing large-scale structure data. To do so, we decouple the linear
growth of density inhomogeneities from the background expansion, and constrain
its redshift dependence making use of a combination of 6 different data sets,
including cosmic shear, galaxy clustering and CMB lensing. We analyze these
data under a consistent harmonic-space angular power spectrum-based pipeline.
We show that current data constrain the amplitude of fluctuations mostly in the
range $0.2<z<0.7$, where it is lower than predicted by \planck. This difference
is mostly driven by current cosmic shear data, although the growth histories
reconstructed from different data combinations are consistent with each other,
and we find no evidence of systematic deviations in any particular experiment.
In spite of the tension with \planck, the data are well-described by the łcdm
model, albeit with a lower value of $S_8\equiv\sigma_8(Ømega_m/0.3)^0.5$. As
part of our analysis, we find constraints on this parameter of
$S_8=0.7769\pm0.0095$ (68\% confidence level), reaching almost percent-level
errors comparable with CMB measurements.
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