Would cover
1. Small shift on WMAP2 error bars due to lensed power spectrum
2. Discussion of n_sAtauombh2 degeneracy with lensing (made worse)
3. Test mock Planck data to see if power spectrum analysis is sufficient or whether nonGaussianities need to be fully modelled
4. Effect of lensing on Planck forecasts
Would include documentation of LensPix simulation code.
Any overlaps with other work/suggestions?
CMB lensing and effect on parameters

 Posts: 1369
 Joined: September 23 2004
 Affiliation: University of Sussex
 Contact:

 Posts: 1369
 Joined: September 23 2004
 Affiliation: University of Sussex
 Contact:
CMB lensing and effect on parameters
I'm not sure when I'm going to get round to writing up the conclusions of this. Here's a summary.
Using the lensed [tex]C_l[/tex] seems to work fine for parameter estimation as long as you compute the theoretical result accurately. In particular the 2ndorder perturbative result (e.g. astroph/0001303) is not accurate enough. Here's a comparison with the correct result
Red is the 2nd order result, and biases parameters for Planck. The blue result is that of astroph/9505109, which is actually pretty much accurate enough for Planck. The very accurate 'correct' result was generated using the Nov 2004 version of CAMB using a new fullsky generalization of the result in astroph/9505109 (work with Anthony Challinor).
Using the accurate [tex]C_l[/tex] calculation, for a typical idealized Plancklike simulation I get parameter constraints for a vanilla model like this:
Here black is analysing the lensed sky with the lensed [tex]C_l[/tex], red is analysing the unlensed sky with the unlensed [tex]C_l[/tex], and blue is the wrong result if you analyse the lensed sky but neglect lensing in the [tex]C_l[/tex] calculation. The lensed results neglects nongaussianity of the lensed field.
[The simulation input model had [tex]n_s = 0.99[/tex], [tex]A_s = 2.5 \times 10^{9}[/tex], [tex]\Omega_b h^2 = 0.022[/tex], [tex]\Omega_b h^2 = 0.12[/tex], [tex]\tau=0.15[/tex] and [tex]h=0.72[/tex]].
Using the lensed [tex]C_l[/tex] seems to work fine for parameter estimation as long as you compute the theoretical result accurately. In particular the 2ndorder perturbative result (e.g. astroph/0001303) is not accurate enough. Here's a comparison with the correct result
Red is the 2nd order result, and biases parameters for Planck. The blue result is that of astroph/9505109, which is actually pretty much accurate enough for Planck. The very accurate 'correct' result was generated using the Nov 2004 version of CAMB using a new fullsky generalization of the result in astroph/9505109 (work with Anthony Challinor).
Using the accurate [tex]C_l[/tex] calculation, for a typical idealized Plancklike simulation I get parameter constraints for a vanilla model like this:
Here black is analysing the lensed sky with the lensed [tex]C_l[/tex], red is analysing the unlensed sky with the unlensed [tex]C_l[/tex], and blue is the wrong result if you analyse the lensed sky but neglect lensing in the [tex]C_l[/tex] calculation. The lensed results neglects nongaussianity of the lensed field.
[The simulation input model had [tex]n_s = 0.99[/tex], [tex]A_s = 2.5 \times 10^{9}[/tex], [tex]\Omega_b h^2 = 0.022[/tex], [tex]\Omega_b h^2 = 0.12[/tex], [tex]\tau=0.15[/tex] and [tex]h=0.72[/tex]].