CAMB: Modifying the Code to Define an Arbitrary w(a)

Use of Cobaya. camb, CLASS, cosmomc, compilers, etc.
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Dror Berechya
Posts: 13
Joined: June 02 2024
Affiliation: Weizmann Institute of Science

CAMB: Modifying the Code to Define an Arbitrary w(a)

Post by Dror Berechya »

Hello everyone,

I have modified the `set_params()` function in `cosmo_packages/code/CAMB/camb/` to define a new dark energy model where the equation of state is described by calling `self.set_w_a_table(a, w)` to effectively represent an arbitrary function for [math].

I have two questions regarding my modification:
  • Is this modification sufficient to describe a new dark energy model that affects only the background dynamics?
  • Is it possible to make this model dependent on sampled parameters that are not traditionally included in an equation for [math], such as [math]? If so, should I do this by including the relevant parameter in the `set_params()` input parameters, or do I need to specify it in other parts of the code?
Thank you very much for your help,
Dror
Antony Lewis
Posts: 1983
Joined: September 23 2004
Affiliation: University of Sussex
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Re: CAMB: Modifying the Code to Define an Arbitrary w(a)

Post by Antony Lewis »

It can't by default depend on cosmological parameters, but you could probably modify the call in camb.set_params to pass additional info. The dependencies can get a bit complicated in general (e.g. if you set thetastar and a dark energy model, some parameters like H0/Omega_m will change depending on the dark energy model at fixed omch2).
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