CMB Lensing and Delensing
The cosmic microwave background is gravitationally lensed by large-scale structure.
This produces distinctive distortions that can be used to reconstruct the lensing
field and learn about cosmology. I'll describe how the Planck satellite has
measured this signal, reconstructing lensing maps and constraining parameters.
Delensing will be important for future CMB observations, and I'll demonstrate
proof-of-principle with the Planck data. Finally, I'll describe some effects that
might limit how well delensing can be achieved in principle, including various
corrections to the "lens remapping" approximation.