Extracting cosmological parameters from a given CMB power spectrum

Use of Healpix, camb, CLASS, cosmomc, compilers, etc.
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Esteban Chalbaud
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Joined: June 01 2019
Affiliation: Master's student
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Extracting cosmological parameters from a given CMB power spectrum

Post by Esteban Chalbaud » July 03 2019

Hello everyone,

I am trying to extract cosmological parameters using CosmoMC, but i am confused in how CosmoMC handles CMB power spectrum, i know that i have to call a given .ini file but do not where i can specify a given power spectrum file, as far as i know the power spectrum is computed by CAMB first, but if i already have the file how i can do that?.

Thanks in advance.

Esteban

Antony Lewis
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Affiliation: University of Sussex
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Re: Extracting cosmological parameters from a given CMB power spectrum

Post by Antony Lewis » July 03 2019

If by spectrum you mean likelihood, you'd need to write your own likelihood or adapt one of the provided ones. If you are unclear of what the difference between a data power spectrum, likelihood or model power spectrum is, I suggest reading some background material on MCMC first.

Esteban Chalbaud
Posts: 6
Joined: June 01 2019
Affiliation: Master's student
Contact:

Re: Extracting cosmological parameters from a given CMB power spectrum

Post by Esteban Chalbaud » July 03 2019

Ok, I was totally wrong.
I know the theoretical difference, but i do not know how to adapt one likelihood to read an specific power spectrum
Is there any material available to do this? I have no idea where to start.
Thank you in advance

Esteban Chalbaud
Posts: 6
Joined: June 01 2019
Affiliation: Master's student
Contact:

Re: Extracting cosmological parameters from a given CMB power spectrum

Post by Esteban Chalbaud » July 03 2019

I think the Planck's likelihood uses the Planck's power spectra, so i was thinking to change this file, in order that Planck's likelihood uses my file instead of the default one, but is not clear for me how does it work in the code or which file i have to change to achieve this.

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