Sachs-Wolfe and Doppler Transfer Functions

Use of Healpix, camb, CLASS, cosmomc, compilers, etc.
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Muhammad Junaid
Posts: 7
Joined: January 05 2017
Affiliation: University of Alberta

Sachs-Wolfe and Doppler Transfer Functions

Post by Muhammad Junaid » January 06 2017

I have been using your 'Camb' code to calculate transfer functions for my research. I am interested in calculation of [tex]T_{SW}(k)[/tex] and [tex]T_{D}(k)[/tex] where these are Sachs-Wolfe and Doppler terms as given in Eq. (7.3.58) DAMPT lectures on cosmology (http://www.damtp.cam.ac.uk/user/db275/Cosmology2015.pdf) so can you help me with that.

I also wanted to know the units of Camb code output velocity transfer functions [tex]vel/k^2[/tex] and if one multiplies [tex]vel/k^2[/tex] by [tex]k^2[/tex] then what will be the units of [tex]vel[/tex] Transfer functions 11, 12 13.

Antony Lewis
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Joined: September 23 2004
Affiliation: University of Sussex
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Re: Sachs-Wolfe and Doppler Transfer Functions

Post by Antony Lewis » January 06 2017

You can get individual terms for the sources by commenting appropriately the terms in output() in equations.f90. Doppler and ISW terms are already there (commented or not).

The transfer functions should be dimensionless (and normalized for unit initial superhorizon curvature perturbation).

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

Sachs-Wolfe and Doppler Transfer Functions

Post by Muhammad Junaid » January 06 2017

So how can i access to value of Doppler term, as I have uncommented the code in output() but i don't see any new result in transfer_function output file. How can I output the doppler term in the transfer function output file.

Secondly, is there any way one can calculate the transfer function without the comoving perturbations [tex]\mathcal{R}_k[/tex] part as in Eq. 7.3.58 of Dampt lectures, [tex]\Theta (k,\hat{n})= [T_{SW}(k)+i \cos(\theta)T_{D}(k)] \mathcal{R}_k[/tex], as I just need [tex]T_{D}[/tex] and [tex]T_{SW}[/tex]. You see, I calculate the power spectrum for the comoving perturbations using my own model (code) and I only need the [tex]T_{SW}[/tex] and [tex]T_{D}[/tex] part of the transfer functions.

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