Weak lensing post-Born effects are equivalent to pure lens-lens couplings

We show that the so-called post-Born effects of weak lensing at 4th order are equivalent to lens-lens couplings in the Born Approximation. We demonstrate this by explicitly showing the equivalence of the canonical weak lensing approach at 4th order using the anisotropy remapping method, to that of the 4th order calculation of the lens-lens coupling effects using the Boltzmann equation approach that was first developed in [1].

Automated summary

This study demonstrates the equivalence between the 4th order calculation of weak lensing effects and the lens-lens coupling effects in the Born Approximation.