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Cobaya: Adding new parameters

Posted: March 04 2021
by David Kniazevas
Hi there,

I am currently working on a small project in which I have obtained a constraint on the volume-averaged angular diameter distance [math] (with the value of 1496 +20 -23) at an effective redshift [math] using the BOSS dataset.

Now I want to use Cobaya to combine this constraint on [math] with the Planck data to obtain constraints on other cosmological parameters, most importantly the dark energy.

However, I have been having trouble figuring out a way to use this [math] parameter in Cobaya. I have so far installed all the cosmological codes and data and used the cosmo-generator to get a yaml file for Planck input with CLASS. Do I now add [math] to the list of all the parameters in the file and specify its priors? Or is it supposed to be a derived parameter? How do I then instruct Cobaya to use [math] in working out the other parameters?

This is my first time using Cobaya so any help and tips would be greatly appreciated. Thank you.


Re: Cobaya: Adding new parameters

Posted: March 05 2021
by Antony Lewis
If you mean DV/r_s, then you just need to add your likelihood nothing else -e.g. adapt the provided sdss_dr7_mgs or sixdf_2001_bao (though you can also add DV as an output derived parameter if you want to)