Speaker
Description
Lensing rotation (or curl lensing or shear B-modes) vanish at leading order in a concordance cosmology. However, it can be produced from sequential lensing events and is therefore a unique post-Born lensing observable. This rotation forms bispectra with other large-scale structure tracers, which can be leveraged to optimally probe the rotation as a cross-spectrum signal. I describe this process for the CMB lensing case, and with the aid of external tracers I will forecast the detection prospects for upcoming CMB experiments the Simons Observatory (SO) and CMB-S4. I also derive an equivalent curl estimator for the curved-sky, and present detailed validation of the methods using mock data from N-body simulations. This will include sensitivities to non-Gaussianities, state-of-the-art iterative lensing estimators, and robustness against extra-galactic foregrounds. I wrap up with some cosmology forecasts that would accompany a CMB curl detection.
