parametrization of Hubble parameter

[Hana Izdi]

i want to add a new parameterization of H(z)**2 = Hfid**2 (A (1+z)**3+ B + Cz + D (1+z)**e)**0.5
to study the evolution of Hubble without too many assuming low redshift physics and recreating the triangle plot of the paramater A, B, C, D, e. this is an expansion of lambdacdm model which is the default in cosmomc. if i want to add that and only using sn and bao data, which file i can modify? indeed, i know where to locate the likelihood for data and new equation but since this is not just adding new likelihood but also modifying the model and i cant find any source on that topic, i am left confused. m sorry for such a lot of question. i am recreating the work previously done by Lemos et al. on model independent H(z) reconstruction.

[Hana Izdi]

Hi, i get a new problem when downloading cosmomc from github, i cant find any files named params.ini, which is the one ishould modify for my parameters, can you tell me whats wrong and how can i solve it?

[Antony Lewis]

You'd either have to change CAMB self-consistently with a modified theory, or modify the likelihoods and/or cosmology wrapper to directly calculate your custom background (and presumably fix r_s for BAO). It would take a bit of work.