### [astro-ph/0610007] Separating the Weak Lensing and Kinetic S

Posted:

**October 05 2006**This paper defines a simple component of the CMB 4-point function which they claim vanishes for lensing but provides a signature of kinetic SZ, hence allowing one to probe the latter independently.

My first comment is that they are using a series expansion in the deflection angle. As they mention this is an approximation, and in fact is not really very good (e.g. see Fig 8 of astro-ph/0601594). However doesn't the lensed < T_lens(x)^3 T_lens(y) > vanish more generally (for uncorrelated lensing potential) because T_lens is linear in T, we assume T is Gaussian and isotropic, and <T(x)^2> is unchanged by lensing?

My second comment is that the SZ signal will be correlated with the lensing signal to some extent (see e.g. astro-ph/0208325), which presumably complicates the picture.

My first comment is that they are using a series expansion in the deflection angle. As they mention this is an approximation, and in fact is not really very good (e.g. see Fig 8 of astro-ph/0601594). However doesn't the lensed < T_lens(x)^3 T_lens(y) > vanish more generally (for uncorrelated lensing potential) because T_lens is linear in T, we assume T is Gaussian and isotropic, and <T(x)^2> is unchanged by lensing?

My second comment is that the SZ signal will be correlated with the lensing signal to some extent (see e.g. astro-ph/0208325), which presumably complicates the picture.