Higher-Order Gravitational Lensing Reconstruction using Feynman Diagrams

Understand

We develop a method for calculating the correlation structure of the Cosmic Microwave Background (CMB) using Feynman diagrams, when the CMB has been modified by gravitational lensing, Faraday rotation, patchy reionization, or other distorting effects.

• This method is used to calculate the bias of the Hu-Okamoto quadratic estimator in reconstructing the lensing power spectrum up to O(\phi^4) in the lensing potential $\phi$.
• We consider both the diagonal noise TTTT, EBEB, etc.
• and, for the first time, the off-diagonal noise TTTE, TBEB, etc.