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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: 39
Affiliation: Oskar Klein Centre, Stockholm University

PostPosted: June 15 2017  Reply with quote

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
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Antony Lewis



Joined: 23 Sep 2004
Posts: 1277
Affiliation: University of Sussex

PostPosted: June 15 2017  Reply with quote

You'd have to write your own prior, e.g. in TP_NonBaseParameterPriors in CosmologyParameterizations.f90.
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Sunny Vagnozzi



Joined: 15 Aug 2016
Posts: 39
Affiliation: Oskar Klein Centre, Stockholm University

PostPosted: June 15 2017  Reply with quote

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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