Statistical Inconsistencies in the KiDS-450 Dataset
  The Kilo-Degree Survey (KiDS) has been used in several recent papers to infer
constraints on the amplitude of the matter power spectrum and matter density at
low redshift. Some of these analyses have claimed tension with the Planck
$\Lambda \mathrm{CDM}$ cosmology at the $\sim 2-3\sigma$ level, perhaps
indicative of new physics. However, Planck is consistent with other low
redshift probes of the matter power spectrum such as redshift space distortions
and the combined galaxy-mass and galaxy-galaxy power spectra. Here we perform
consistency tests of the KiDS data, finding internal tensions for various cuts
of the data at $\sim 2.2 - 3.5\sigma$ significance. Until these internal
tensions are understood, we argue that it is premature to claim evidence for
new physics from KiDS. We review the consistency between KiDS and other weak
lensing measurements of $S_8$, highlighting the importance of intrinsic
alignments for precision cosmology.
