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Muhammad Junaid
Joined: 05 Jan 2017 Posts: 7 Affiliation: University of Alberta

Posted: March 28 2017 


Hi everyone,
I just have one simple question question, I want to calculate the temperature anisotropies as a function of wave number i.e. ΔT(k) / T using the list of transfer functions output from the camb code. I just want to use my own initial power spectrum P_{ζ}(k) of initial perturbations(comoving curvature perturbations) to calculate . Where Δ_{i}(k) would be some combination of transfer functions of the camb code. So, what precise combinations of transfer functions do I need here as Δ_{i}'s?
Thanks in Advance!!
M Junaid 

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Antony Lewis
Joined: 23 Sep 2004 Posts: 1303 Affiliation: University of Sussex

Posted: March 28 2017 


Are you sure you don't want to calculate the C_{} power spectrum? That's easily done by modifying CAMB's power_tilt.f90 to use your own initial power spectrum (and increasing accuracy settings if needed). 

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Muhammad Junaid
Joined: 05 Jan 2017 Posts: 7 Affiliation: University of Alberta

Posted: March 28 2017 


No we are working out some moments in momentum space so we don't need C_{l} or any angular part. 

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Muhammad Junaid
Joined: 05 Jan 2017 Posts: 7 Affiliation: University of Alberta

Posted: March 30 2017 


My hunch is that the temperature anisotropy is to leading order equal to , where Φ is Weyl potential. While, you have said in your notes that power spectrum of Weyl potential is P_{Φ} = T_{Φ}(k)P_{ζ}(k) where ζ is primordial perturbations. Is the same true for other power spectra as . So the transfer function output from the camb code are that don't include the primordial power spectrum P_{ζ}(k). Please correct me if I am wrong!
M. 

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Antony Lewis
Joined: 23 Sep 2004 Posts: 1303 Affiliation: University of Sussex

Posted: March 30 2017 


Transfer function outputs are not squared (and indeed not scaled by the primordial power). The temperature sources are quite complicated in general (calculated in output routine of equations.f90). 

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