CosmoMC: computing H from theta

Use of Healpix, camb, CLASS, cosmomc, compilers, etc.
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Jim Cline
Posts: 5
Joined: October 06 2005
Affiliation: McGill University

CosmoMC: computing H from theta

Post by Jim Cline » October 19 2005

Using the theta, tau parametrization of CosmoMC, is there an easy way to compute
the corresponding Hubble parameter, given a complete set of the other cosmological
parameters? Before writing my own code to do this, I want to be sure it's not already
buried somewhere in the CosmoMC source code.

Antony Lewis
Posts: 1511
Joined: September 23 2004
Affiliation: University of Sussex
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Re: CosmoMC: computing H from theta

Post by Antony Lewis » October 20 2005

The code for this is in params_CMB.f90 (it does a binary search to find the right value, so not totally trivial).

Note that if you run chains the program automatically outputs H as a derived parameter in the chain files, so there's not usually any need to convert manually.

Jim Cline
Posts: 5
Joined: October 06 2005
Affiliation: McGill University

CosmoMC: computing H from theta

Post by Jim Cline » October 25 2005

Thanks Antony. At the moment I am only running chains of length 1, or else
searching for the maximum likelihood point, while I gear up to do MPI runs,
so H has not been output automatically. Now I've fixed that.

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