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Putting a hard prior on w0+wa
 
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Sunny Vagnozzi



Joined: 15 Aug 2016
Posts: 32
Affiliation: Oskar Klein Centre, Stockholm University

PostPosted: June 29 2017  Reply with quote

Dear Anthony et al.,

I am running chains with the CPL parametrization w(z)=w0+wa*(1-a).

However, I am thinking of this parametrization in the context of quintessence (scalar field) dark energy models which mean w(z)>−1 for all z, which translates to w0+wa>−1. I want to impose this condition as a hard prior.

In CosmologyParametrizations.f90, within the function TP_NonBaseParameterPriors, I wrote the following:
Code:
if (CMB%wa + CMB%w < -1.0) return

which is supposed to return logZero=1030 (i.e. a very high chi2) if w0+wa<−1

However, I noticed that my chains are still accepting points with w0+wa<−1 (not much smaller than −1, like −1.02 or so, but nonetheless the hard prior should cut these points out). Do you have any idea if and where my mistake is? The above is the only change I made in the source folder.

Thanks a lot! Cheers,
Sunny
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Cosmo Xu



Joined: 19 Mar 2013
Posts: 4
Affiliation: NJU/NAOC

PostPosted: June 30 2017  Reply with quote

Hi,

Have you checked the chi2 value for those points with w0+wa<−1?
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Sunny Vagnozzi



Joined: 15 Aug 2016
Posts: 32
Affiliation: Oskar Klein Centre, Stockholm University

PostPosted: June 30 2017  Reply with quote

Actually it seems to work now, so the problem should be solved!
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