Page 1 of 1

CAMB: calculating derivatives of Cl''s wrt parameters

Posted: August 08 2017
Is there any way to have CAMB calculate derivatives of CMB power spectra with respect to cosmological parameters? I.e. quantities like $$\frac{\partial C_{\ell}}{\partial(\Omega_ch^2)}$$

I can numerically estimate derivatives by perturbing parameters and re-running but wanted to check if there's some better / more efficient way.

Thanks

Re: CAMB: calculating derivatives of Cl''''s wrt parameters

Posted: August 09 2017
That's usually the best way. (unless you really want parameter errors/forecasts - in which case run CosmoMC).

CAMB: calculating derivatives of Cl''s wrt parameters

Posted: August 10 2017
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?

Re: CAMB: calculating derivatives of Cl''''s wrt parameters

Posted: August 10 2017
You probably could, but it might take some thought on how to code it.

CAMB: calculating derivatives of Cl''s wrt parameters

Posted: August 10 2017
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.