Camb AxionEffectiveFluid dark energy model
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- Posts: 3
- Joined: May 01 2020
- Affiliation: CNRS LAL IJClab
Camb AxionEffectiveFluid dark energy model
Hi !
I'm trying to use the AxionEffectiveFluid dark energy model from CAMB to generate spectra.
class camb.dark_energy.AxionEffectiveFluid[source]
Bases: camb.dark_energy.DarkEnergyModel
Variables:
w_n – (float64)
om – (float64)
a_c – (float64)
theta_i – (float64)
I noticed that varying the om parameter seems to change the value of [math]. But I fixed this parameter while declaring the cosmology parameters. Do you know why the spectra are modified this way ?
Thanks for your future answsers
Adrien
I'm trying to use the AxionEffectiveFluid dark energy model from CAMB to generate spectra.
class camb.dark_energy.AxionEffectiveFluid[source]
Bases: camb.dark_energy.DarkEnergyModel
Variables:
w_n – (float64)
om – (float64)
a_c – (float64)
theta_i – (float64)
I noticed that varying the om parameter seems to change the value of [math]. But I fixed this parameter while declaring the cosmology parameters. Do you know why the spectra are modified this way ?
Thanks for your future answsers
Adrien
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- Posts: 1944
- Joined: September 23 2004
- Affiliation: University of Sussex
- Contact:
Re: Camb AxionEffectiveFluid dark energy model
Theta_MC is an approximation for standard cosmologies. Better to fix thetastar in this case if you want the sound horizon to actually stay constant (see https://camb.readthedocs.io/en/latest/model.html#camb.model.CAMBparams.set_cosmology).
-
- Posts: 3
- Joined: May 01 2020
- Affiliation: CNRS LAL IJClab
Re: Camb AxionEffectiveFluid dark energy model
Hi !
I tried to keep thetastar constant, but the two spectra are still moving the same way. I put the script I used in attached files (sorry for the .zip, i could not attach a .py file)
I tried to keep thetastar constant, but the two spectra are still moving the same way. I put the script I used in attached files (sorry for the .zip, i could not attach a .py file)
-
- Posts: 1944
- Joined: September 23 2004
- Affiliation: University of Sussex
- Contact:
Re: Camb AxionEffectiveFluid dark energy model
If you change the dark energy model, you need to do so *before* calling set_cosmology if you are using cosmomc_theta or thetastar (because the solution for H0 to give required thetastar depends on the dark energy model). Alternatively use camb.set_params, e.g.
Also your fluid om values are probably far too large to get a valid H0 solution, since this model decays rapidly at late times.
Code: Select all
pars = camb.set_params(dark_energy_model='AxionEffectiveFluid', thetastar=...)
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- Posts: 3
- Joined: May 01 2020
- Affiliation: CNRS LAL IJClab
Re: Camb AxionEffectiveFluid dark energy model
Thanks for this answer. I tried and it seems to be working, it was very helpful !