CAMB: calculating derivatives of Cl's wrt parameters

 Posts: 33
 Joined: July 17 2014
 Affiliation: Johns Hopkins University
CAMB: calculating derivatives of Cl''s wrt parameters
Is there any way to have CAMB calculate derivatives of CMB power spectra with respect to cosmological parameters? I.e. quantities like [tex]\frac{\partial C_{\ell}}{\partial(\Omega_ch^2)}[/tex]
I can numerically estimate derivatives by perturbing parameters and rerunning but wanted to check if there's some better / more efficient way.
Thanks
I can numerically estimate derivatives by perturbing parameters and rerunning but wanted to check if there's some better / more efficient way.
Thanks

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 Joined: September 23 2004
 Affiliation: University of Sussex
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Re: CAMB: calculating derivatives of Cl''''s wrt parameters
That's usually the best way. (unless you really want parameter errors/forecasts  in which case run CosmoMC).

 Posts: 33
 Joined: July 17 2014
 Affiliation: Johns Hopkins University
CAMB: calculating derivatives of Cl''s wrt parameters
OK. How about if I want to evaluate these derivatives at each step of a CosmoMC chain? Can I have CAMB called multiple times at each step with slightly different parameters?

 Posts: 1646
 Joined: September 23 2004
 Affiliation: University of Sussex
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Re: CAMB: calculating derivatives of Cl''''s wrt parameters
You probably could, but it might take some thought on how to code it.

 Posts: 33
 Joined: July 17 2014
 Affiliation: Johns Hopkins University
CAMB: calculating derivatives of Cl''s wrt parameters
Hmm OK. I think I'll start with figuring out how much the derivatives are really varying in case I don't need to do the recalculation each step. Thanks.