The skewed weak lensing likelihood: why biases arise, despite data and theory being sound

Understand

We derive the essentials of the skewed weak lensing likelihood via a simple Hierarchical Model.

• Our likelihood passes four objective and cosmology-independent tests which a standard Gaussian likelihood fails.
• We demonstrate that sound weak lensing analyses are naturally biased low, and this does not indicate any new physics such as deviations from $\Lambda$CDM.
• Mathematically, the biases arise because noisy two-point functions follow skewed distributions.