CAMB - Help with Transfer Function Outputs

Use of Healpix, camb, CLASS, cosmomc, compilers, etc.
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Himanish Ganjoo
Posts: 2
Joined: February 26 2016
Affiliation: BITS Pilani

CAMB - Help with Transfer Function Outputs

Post by Himanish Ganjoo » February 28 2016

I am sorry if this is a trivial question, but I am new to CAMB and I am trying to figure out the transfer function output file.

One output file generated is the output_root_transfer.dat, which contains transfer functions for various quantities.

The CAMB readme says that the columns contain:
k/h , \Delta / k^2 and so on...

My query is, how do I get the power spectrum from these values?

If the second column has \Delta/k^2, I thought multiplying by k^2 would get me \Delta, and then squaring it would give me the dimensionless power spectrum, from which I can get the power spectrum:
P(k) = 2\pi^2 \Delta^2 / k^3

However, this does not seem to generate the well-known shape of the power spectrum.

Any help on what exactly the output file contains would help me a great deal.

Antony Lewis
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Joined: September 23 2004
Affiliation: University of Sussex
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Re: CAMB - Help with Transfer Function Outputs

Post by Antony Lewis » February 28 2016

The docs are correct. The CAMB notes give some relations between different power spectra definitions:
http://cosmologist.info/notes/CAMB.pdf

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