Adding Hdot to the background and perturbations in CAMB

Use of Cobaya. camb, CLASS, cosmomc, compilers, etc.
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Maryam A. Abchouyeh
Posts: 2
Joined: February 12 2024
Affiliation: IUT

Adding Hdot to the background and perturbations in CAMB

Post by Maryam A. Abchouyeh » February 12 2024

Hi,

I am trying to modify CAMB for a cosmological model that includes Hdot in the first Friedman equation, with an additional constant coefficient.
As I understand, first of all I should change dtauda in equation.f90, but to modify the code properly, at least results.f90 and inidriver.f90 should also be modified.
Would you please let me know which part of these three files should be changed to create a reliable result?
And is there any other file that needs a modification accordingly?

Thanks

Antony Lewis
Posts: 1930
Joined: September 23 2004
Affiliation: University of Sussex
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Re: Adding Hdot to the background and perturbations in CAMB

Post by Antony Lewis » February 12 2024

The background equations are also used in derivs() for the perturbations. However, if the background Einstein equation changes, usually the perturbed one does as well, so you'd need to modify the perturbation equations consistently anyway. Depending on your particular model, and what outputs you want to calculate, you'll have to go through the code checking relevant things that have changed.

Maryam A. Abchouyeh
Posts: 2
Joined: February 12 2024
Affiliation: IUT

Re: Adding Hdot to the background and perturbations in CAMB

Post by Maryam A. Abchouyeh » February 12 2024

Antony Lewis wrote:
February 12 2024
The background equations are also used in derivs() for the perturbations. However, if the background Einstein equation changes, usually the perturbed one does as well, so you'd need to modify the perturbation equations consistently anyway. Depending on your particular model, and what outputs you want to calculate, you'll have to go through the code checking relevant things that have changed.
Thanks.
Equations for perturbations are only in drives(), or I should also look for them in other files?

Antony Lewis
Posts: 1930
Joined: September 23 2004
Affiliation: University of Sussex
Contact:

Re: Adding Hdot to the background and perturbations in CAMB

Post by Antony Lewis » February 13 2024

derivs for evolution, there's also initial conditions in equations.f90. And the NonLinear model for late-time lensing etc.

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