CosmoMC: non-rectangular boundaries for parameters

Use of Cobaya. camb, CLASS, cosmomc, compilers, etc.
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Pavluchenko Sergey
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Joined: June 21 2005
Affiliation: Phys. Dept., University of Alberta
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CosmoMC: non-rectangular boundaries for parameters

Post by Pavluchenko Sergey » June 27 2007

Hello !

I want to use CosmoMC to obtain constraints for three parameters (fast, user-defined), say, A, B and C. Two of them - A and B - have rectangular boundaries, so I can define them in params.ini in usual way. But third - C - have boundaries which are functions of A and B (and A and B only). So can anyone give me an advice about how can one modify the code in order to use curved boundaries ?

Thanks in advance !

Anze Slosar
Posts: 183
Joined: September 24 2004
Affiliation: Brookhaven National Laboratory
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CosmoMC: non-rectangular boundaries for parameters

Post by Anze Slosar » June 27 2007

Put a very large flat prior on C in the params.ini and the change likelihood routine so that it returns 1e30 every time proposed C is out of boundaries determined by A and B.
However, not that such scenario usually have strong implied priors. You better run your code without data, just to see the implied "constraint" on C.

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