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 How to put a hard prior on w_de with CPL equation of state parametrization?
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Sunny Vagnozzi

Joined: 15 Aug 2016
Posts: 41
Affiliation: Oskar Klein Centre, Stockholm University

Posted: June 15 2017

Dear Anthony et al,

say I am using the CPL parametrization for the dark energy equation of state (or for that matter, any other 2-parameter parametrization of the equation of state), which is implemented in line 98 of camb/equations_ppf.f90:
 Code: w_de=w_lam+wa_ppf*(1._dl-a)

If I understand this correctly, I can then put hard priors on wlam and wa_ppf through param[w]= and param[wa]= in my ini file. Is this correct so far?

However, say I want to put a hard prior on wde instead (which is given by the combination of w and wa if I understood this correctly), say e.g. I want wde>−1 because I am studying a quintessence model, how do I impose this?

Thanks a lot! Cheers,
Sunny
Antony Lewis

Joined: 23 Sep 2004
Posts: 1309
Affiliation: University of Sussex

 Posted: June 15 2017 You'd have to write your own prior, e.g. in TP_NonBaseParameterPriors in CosmologyParameterizations.f90.
Sunny Vagnozzi

Joined: 15 Aug 2016
Posts: 41
Affiliation: Oskar Klein Centre, Stockholm University

Posted: June 15 2017

Dear Anthony,

thanks for your help! I looked into TP_NonBaseParameterPriors. Would it be sufficient to have something like:
 Code: if (CMB%w_de < -1.0) return

assuming I want to set wde>−1? Would this ensure that wde would be −1 for any value of redshift z>0?

Cheers,
Sunny
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