MCMC: How to improve the plots?

Use of Healpix, camb, CLASS, cosmomc, compilers, etc.
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Jun-Qing Xia
Posts: 22
Joined: January 02 2005
Affiliation: SISSA, Italy

MCMC: How to improve the plots?

Post by Jun-Qing Xia » August 04 2005

Dear all,

I use MPI to run CosmoMC and the program now stops automatically. But in the 1D marginalized plots the dotted lines distinctly separate from the solid lines. The CosmoMC Readme says there is a much better fit in a small region of parameter space.
How to improve the result to fit much better? Which parameter should be modified?

Thanks!

Jun-Qing

Antony Lewis
Posts: 1495
Joined: September 23 2004
Affiliation: University of Sussex
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Re: MCMC: How to improve the plots?

Post by Antony Lewis » August 04 2005

Dotted lines are mean likelihoods, solid lines are marginalized probabilities. As discussed in the cosmomc paper (astro-ph/0205436) for non-Gaussian distributions these are different. i.e. your result is probably correct as the posterior distribution is in general non-Gaussian.

The distribution may be more Gaussian if you add more data - e.g. HST or BBN prior, SDSS, etc.

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