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CAMB - Help with Transfer Function Outputs
 
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Himanish Ganjoo



Joined: 26 Feb 2016
Posts: 2
Affiliation: BITS Pilani

PostPosted: February 28 2016  Reply with quote

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 , Δ / k2 and so on...

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

If the second column has Δ/k2, I thought multiplying by k2 would get me Δ, and then squaring it would give me the dimensionless power spectrum, from which I can get the power spectrum:
P(k) = 2π2 Δ2 / k3

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.
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Antony Lewis



Joined: 23 Sep 2004
Posts: 1351
Affiliation: University of Sussex

PostPosted: February 28 2016  Reply with quote

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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