Comparison of CAMB with CMB fast

Use of Healpix, camb, CLASS, cosmomc, compilers, etc.
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Daniel Grin
Posts: 11
Joined: April 10 2009
Affiliation: KICP

Comparison of CAMB with CMB fast

Post by Daniel Grin » April 10 2009

I am modifying cosmological recombination histories to include new atomic physics affects, and as a test case decided to compare CMBfast with CAMB with a standard recombination history.

I made sure that I am using the same values of all densities, the Hubble parameter, neutrino parameters, lmax, and (k\eta)_{max}. I used the more up-to-date version of RECFAST in the most recent CMBFAST version and force-fed it (through a file output and read) to CAMB, to do a 'fair comparison', with both codes using the same recombination code.

I get a 1% discrepancy between my TT and EE power spectrum (scalars only), unlike the quoted discrepancy on the CAMB web site of 0.1%-0.3%, when CAMB runs with the highest possible precision settings.

This discrepancy seems to hold for the COBE-unnormalized LOS integrals.

Has anyone run into a similar problem, and if so, has anyone identified the origin of the discrepancy?

Antony Lewis
Posts: 1592
Joined: September 23 2004
Affiliation: University of Sussex

Re: Comparison of CAMB with CMB fast

Post by Antony Lewis » April 10 2009

Maybe difference in optical depth -> z_re mapping?

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