How to include BKP likelihood in Cosmomc?

 Posts: 14
 Joined: May 12 2016
 Affiliation: HK
How to include BKP likelihood in Cosmomc?
Hi, all. I have a question about BKP likelihood. I am trying to constrain the tensor amplitude in my model. I find a very strange thing. When I include all Planck likelihood (all the four likelihoods of Planck) AND the BKP likelihood, the tensor amplitude has a nonzero preferred value. This is not reasonable and I think all the model should prefer a zero tensor amplitude currently. When I include Planck likelihood OR BKP likelihood separately, the result is reasonable and a zero value tensor amplitude is more preferred. So, why a nonzero value is preferred when I combine Planck and BKP? Is there a conflict between them? Or are there non trivial settings in the .ini file? BTW, does the covmat matter in the settings?
Thanks a lot! Can some experienced persons explain it or give me some instructions? Thanks again.
Thanks a lot! Can some experienced persons explain it or give me some instructions? Thanks again.

 Posts: 53
 Joined: August 15 2016
 Affiliation: Kavli Institute for Cosmology (KICC), University of Cambridge
How to include BKP likelihood in Cosmomc?
Dear Jack,
first of all, what do you mean that you are including all four Planck likelihoods? Do you mean plik_dx11dr2_HM_v18_TT.ini , plik_dx11dr2_HM_v18_TTTEEE.ini , lowTEB.ini , and lowl.ini? If this is the case, that would be incorrect since you would be doublecounting information, I believe you should only add two of these at a time, e.g. for what Planck calls PlanckTT+lowP, you would add plik_dx11dr2_HM_v18_TT.ini and lowTEB.ini, etc. This is the first point.
Second, I don't think a (small) preference for a nonzero tensortoscalar ratio is a big problem. As long as it is preferred at only say 1 sigma or so, I think that's not a huge problem.
Finally, in your distparams.ini, did you set limits[r] = 0 N? Because if you didn't do so, that would easily explain your error. You must do this for any parameter for which the prior cuts at a value where the posterior is nonnegligible, and the tensortoscalar ratio is an example of these. Please see th CosmoMC README for more information.
Cheers,
Sunny
first of all, what do you mean that you are including all four Planck likelihoods? Do you mean plik_dx11dr2_HM_v18_TT.ini , plik_dx11dr2_HM_v18_TTTEEE.ini , lowTEB.ini , and lowl.ini? If this is the case, that would be incorrect since you would be doublecounting information, I believe you should only add two of these at a time, e.g. for what Planck calls PlanckTT+lowP, you would add plik_dx11dr2_HM_v18_TT.ini and lowTEB.ini, etc. This is the first point.
Second, I don't think a (small) preference for a nonzero tensortoscalar ratio is a big problem. As long as it is preferred at only say 1 sigma or so, I think that's not a huge problem.
Finally, in your distparams.ini, did you set limits[r] = 0 N? Because if you didn't do so, that would easily explain your error. You must do this for any parameter for which the prior cuts at a value where the posterior is nonnegligible, and the tensortoscalar ratio is an example of these. Please see th CosmoMC README for more information.
Cheers,
Sunny

 Posts: 53
 Joined: August 15 2016
 Affiliation: Kavli Institute for Cosmology (KICC), University of Cambridge
How to include BKP likelihood in Cosmomc?
I would also suggest having a read at batch2/BK14_README.txt

 Posts: 31
 Joined: August 14 2016
 Affiliation: IIT Bombay
How to include BKP likelihood in Cosmomc?
Doesn't the Nov 2016 version of CosmoMC automatically add the limits[r] = 0 N? (In the .derived_ranges files (in /paramnames folder), see Version History section)

 Posts: 53
 Joined: August 15 2016
 Affiliation: Kavli Institute for Cosmology (KICC), University of Cambridge
How to include BKP likelihood in Cosmomc?
Yes it should

 Posts: 53
 Joined: August 15 2016
 Affiliation: Kavli Institute for Cosmology (KICC), University of Cambridge
How to include BKP likelihood in Cosmomc?
The default distparams.ini I believe also has this setting