It is currently Tue Nov 30, 2021 4:55 pm

All times are UTC - 8 hours [ DST ]




Post new topic Reply to topic  [ 9 posts ] 
Author Message
PostPosted: Fri Nov 05, 2010 1:58 am 
Offline

Joined: Wed May 17, 2006 7:02 am
Posts: 285
Location: MPE Garching
a new paper on using galprop in a multinested Bayesian code is at
http://arxiv.org/abs/1011.0037

the supplementary data (galdef files, parameter chains, data files) can be found at see http://www.g-vo.org/pub/GALPROP

_________________
Andy Strong, MPE


Top
 Profile  
 
PostPosted: Wed Nov 17, 2010 5:02 am 
Offline

Joined: Mon Jan 19, 2009 9:48 am
Posts: 19
Location: INFN Perugia
Results on the propagation parameters are given in terms of Best-Fit (i.e. from Chi^2 minimization) and Posterior-Mean (i.e. expectation values of the posterior pdf's). In some cases they differ a lot. So...stupid question: which one really "matters"? What's the "ultimate" set of CR propagation parameter that can be determined (with Galprop) at best of our knowledge on the basis of existing data? BestFit (as I'd guess) or PosteriorMean ? Why have you quoted both...do I miss some relevant physical differences/complementarity in the two?


Top
 Profile  
 
PostPosted: Wed Nov 17, 2010 5:07 am 
Offline

Joined: Wed May 17, 2006 7:02 am
Posts: 285
Location: MPE Garching
(NB they are not chi^2 but probabilities)
The posterior mean is definitely the one to use since it takes account of the full posterior, whereas the maximum posterior could be a local maximum or a narrow peak with little probability content.
Why we quote both: to illustrate the difference.
There is no 'ultimate' parameter set since we only considered a particular class of models, and did not include e.g. convection and other effects, or some other types of data which will give more constraints e.g. pbar (but we intend to in future).

_________________
Andy Strong, MPE


Top
 Profile  
 
PostPosted: Wed Nov 17, 2010 5:22 am 
Offline

Joined: Mon Jan 19, 2009 9:48 am
Posts: 19
Location: INFN Perugia
So.. the fact that the best-fit parameters are within the uncertainty band of the posterior pdfs is to be taken as a remarkable/untrivial result. Is that correct?


Top
 Profile  
 
PostPosted: Wed Nov 17, 2010 5:27 am 
Offline

Joined: Wed May 17, 2006 7:02 am
Posts: 285
Location: MPE Garching
not at all remarkable, this happens in well-behaved distributions, which we have here.

_________________
Andy Strong, MPE


Top
 Profile  
 
PostPosted: Wed Nov 17, 2010 6:30 am 
Offline

Joined: Mon Jan 19, 2009 9:48 am
Posts: 19
Location: INFN Perugia
Ok... thank you very much.


Top
 Profile  
 
PostPosted: Sun Nov 21, 2010 11:08 am 
Offline

Joined: Mon Jan 19, 2009 9:48 am
Posts: 19
Location: INFN Perugia
Another point. In that paper, the fragmentation chain starts from Max_Z = 14 (silicon). So I deduce that the quantities under study (B/C, 10Be/9Be, pbar/p) are not significantly affected by the presence of Z>14 nuclei... correct? If yes... can you quantify "not significantly" with some number? 1%?


Top
 Profile  
 
PostPosted: Sun Nov 21, 2010 11:13 am 
Offline

Joined: Wed May 17, 2006 7:02 am
Posts: 285
Location: MPE Garching
It is completely negligible, certainly below 1%

_________________
Andy Strong, MPE


Top
 Profile  
 
PostPosted: Mon Nov 22, 2010 1:09 am 
Offline
Site Admin

Joined: Wed Oct 21, 2009 6:30 pm
Posts: 47
Location: Stanford U.
I recently tested it by making several runs in WebRun with different max_Z. I was using the "Conventional Model" example. I also stopped at max_Z=14, because the spectra in QuickPlots for B/C and 10Be/9Bebecame indistinguishable from higher max_Z at this point. Certainly well within the uncertainty in the experimental data.

_________________
Andrey Vladimirov
http://galprop.stanford.edu/


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 9 posts ] 

All times are UTC - 8 hours [ DST ]


Who is online

Users browsing this forum: Bing [Bot] and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group