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 Difference between CAMB and WMAP3 (Pt. II)
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A Stewart

Joined: 27 Sep 2007
Posts: 5
Affiliation: McGill University

Posted: October 12 2007

Hi all,

I am new to CAMB and as a test I am just trying to reproduce the WMAP3 results for lcdm+tens model using the parameters given here.

When I plot the totCls.dat file output by CAMB along with the one given on the LAMBDA website I see a large difference around l<100. Can anyone explain whether this is normal or suggest a fix?

I have changed both k_0_scalar and k_0_tensor to 0.002 in power_tilt.f90. I am taking nT = -r / 8.

Here is my params.ini file:

Ben Gold

Joined: 25 Sep 2004
Posts: 97
Affiliation: University of Minnesota

 Posted: October 14 2007 The parameters given in the table aren't for the "best-fit" $C_\ell$, they're the means over the chain. For LCDM+tens the best-fit model has a slightly smaller ΩΛ, closer to 0.777 (not 0.803, which is the mean), which explains the difference at low $\ell$. If you really want the "best-fit" parameters you'll need to download the chain files.
A Stewart

Joined: 27 Sep 2007
Posts: 5
Affiliation: McGill University

 Posted: October 15 2007 So, I guess that will involve running getdist from the COSMOMC package on those chain files. Is there anywhere that the actual "best-fit" parameters used are summarzied without having to install COSMOMC? Sorry I think I should have posted this in the software thread.
Ben Gold

Joined: 25 Sep 2004
Posts: 97
Affiliation: University of Minnesota

Posted: October 23 2007

The best-fit isn't hard to find from the chain files, just look for the line with the lowest -ln(L) and read off the parameters. From the command line you can do something like
 Code: sort -n -k 2 chainfile.txt | head -1

I'll make the suggestion that in the future the best-fit params be summarized somewhere more obvious.
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