CAMB: Lensing potential power spectrum
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CAMB: Lensing potential power spectrum
Does the Lensing potential power spectrum [tex] C_l^{\phi}[/tex] that CAMB churns out include nonlinear corrections from halofit?
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Re: CAMB: Lensing potential power spectrum
Not by default, but you can set do_nonlinear = 2 in the .ini file to add corrections.
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Re: CAMB: Lensing potential power spectrum
Hi Antony,Antony Lewis wrote:Not by default, but you can set do_nonlinear = 2 in the .ini file to add corrections.
When I plot [tex]\ell^4 C_\ell^{\phi\phi} [/tex] vs. [tex]\ell[/tex] with do_nonlinear=0 and do_nonlinear=2 I get almost identical plots:
When I do my own Limber approximation based calculation using the power spectrum from CAMB I get the non-linear potential power spectra to be appreciably higher than the linear case for high l's. I think that should be the case. Am I missing something here?
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Re: CAMB: Lensing potential power spectrum
Probably not using high enough k_eta_max_scalar ? (note CMB lensing for non-BB is insensitive to the high l part of the lensing potential power spectrum; you need k_eta_max_scalar much higher to get the lensing potential accurately than you do to get the lensed C_l accurately)
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CAMB: Lensing potential power spectrum
Hello,
I'm simulating the lensed CMB in a similar way as Lenspix for my Bachelor Thesis.
Using the HEALPix routine synfast I have calculated the gradient of the lensing potential given by CAMB and as next the C_l^dd of the absolute value of the deflection angle. In the ReadMe file of CAMB, they say
C_l^{dd}= [l(l+1)]^2 /(2\pi) Cl^{\Phi\Phi},
where the C_l^{dd} given as output here is equivalent to (l(l+1)) /(2\pi) * C_l(computed)^{dd} , which is my computed deflection angle power spectrum, right?.
But if I plotting this relation, I get a great difference between both! (uploaded figure plot4.eps).
I don't understand the problem, since it seems that my results of the deflection angles are right (going on with the remapping, the produced lensed temperature power spectra fits very well with the theoretical of CAMB).
I wonder if I have a false interpretation of the information given in the ReadMe?
Thanks for the help in anticipation!
Gabriela
I'm simulating the lensed CMB in a similar way as Lenspix for my Bachelor Thesis.
Using the HEALPix routine synfast I have calculated the gradient of the lensing potential given by CAMB and as next the C_l^dd of the absolute value of the deflection angle. In the ReadMe file of CAMB, they say
C_l^{dd}= [l(l+1)]^2 /(2\pi) Cl^{\Phi\Phi},
where the C_l^{dd} given as output here is equivalent to (l(l+1)) /(2\pi) * C_l(computed)^{dd} , which is my computed deflection angle power spectrum, right?.
But if I plotting this relation, I get a great difference between both! (uploaded figure plot4.eps).
I don't understand the problem, since it seems that my results of the deflection angles are right (going on with the remapping, the produced lensed temperature power spectra fits very well with the theoretical of CAMB).
I wonder if I have a false interpretation of the information given in the ReadMe?
Thanks for the help in anticipation!
Gabriela
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- Joined: September 23 2004
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Re: CAMB: Lensing potential power spectrum
"absolute value of the deflection angle"? You don't want [tex]|\nabla\psi|[/tex], but the power spectrum of the gradient (E)-mode part of spin-1 harmonic transform of the map of [tex]\nabla\psi[/tex] (see e.g. appendix of astro-ph/0502469)