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.