Rotation of the CMB polarisation by foreground lensing
  We investigate the weak lensing corrections to the CMB polarization
anisotropies. We concentrate on the effect of rotation and show that the
rotation of polarisation is a true physical effect which has to be taken into
account at second order in perturbation theory. We clarify inconsistencies on
the treatment of this rotation in the recent literature. We also show that at
first order in perturbation theory there is no rotation of polarisation also
for vector and tensor modes.
