[Mesa-users] Adding a new particle species

[Francis Timmes]

if by pair production you mean thermal neutrino processes like e+ + e- -> nu_e + nubar_e,
then the useful if blunt 

% grep -r -I "pair neutrino" $MESA_DIR

can be refined with practice to 

% grep -r -I --exclude-dir={gyre,adipls,stella,website,crlibm,binary,data,const,num,mtx,star,kap,interp_2d,eos} —exclude= \*~,\*.log,make,\*.txt,test_output,\*.data,\*.dat,\*.tbl,\*.mod,\*.phx,\*.atm,\*.rb} "pair neutrino" $MESA_DIR

fxt






> On Aug 19, 2019, at 6:45 PM, Jeremy Sakstein <sakstein at sas.upenn.edu> wrote:
> 
> Thanks Frank, that looks like what I’m looking for. 
> 
> For reference, where in the code would I find the rate for pair production?
> 
> Cheers,
> 
> Jeremy 
> 
> On Mon, Aug 19, 2019 at 9:37 PM Francis Timmes <fxt44 at mac.com> wrote:
> take a look at zetner & hearin’s contribution: 
> https://zenodo.org/record/2590829
> 
> while dated and would need to be brought up-to-date,
> it may contain some useful clues on how to proceed.
> 
> fxt
> 
> 
> 
> > On Aug 19, 2019, at 4:13 PM, Jeremy Sakstein <sakstein at sas.upenn.edu> wrote:
> > 
> > Thanks Frank. 
> > 
> > Yes, it is indeed dark matter. I had a look at the axion cooling test suite but it seems to treat it as a loss by adding an extra source of neutrinos. 
> > 
> > I think I could use this to put the production rate in but am I right in that the end products will, for all intents and purposes, escape the star?
> > 
> > Cheers,
> > 
> > Jeremy 
> > 
> > On Mon, Aug 19, 2019 at 6:27 PM Francis Timmes <fxt44 at mac.com> wrote:
> > seems like aspects of dark matter. if you peruse the inlist and add-ons at mesatsar.org,
> > i believe there are a few contributions that do dark matter in their run_star_extras.
> > 
> > fxt
> > 
> > 
> > 
> > > On Aug 19, 2019, at 2:11 PM, Jeremy Sakstein <sakstein at sas.upenn.edu> wrote:
> > > 
> > > So looking at this, I am not sure that the nets are exactly what I am looking for.
> > > 
> > > Essentially, I would like to add a reaction where a photon combines with an electron to produce a heavy species (this would only happen at super-high temperatures of course) and then the heavy species remains in the core and contributes to the gravity but not the pressure i.e. there is no need to include it in the rates. The nearest thing to this I think is pair production but I can't seem to find where this is implemented. One idea I had was to use other neutrinos but I think this would not give me what I am looking for.
> > > 
> > > Do you have any suggestions?
> > > 
> > > Cheers,
> > > 
> > > Jeremy
> > > 
> > > On Mon, Aug 19, 2019 at 2:35 PM Jeremy Sakstein <sakstein at sas.upenn.edu> wrote:
> > > Thanks Amber!
> > > 
> > > I will take a look at what you suggest.
> > > 
> > > Cheers,
> > > 
> > > Jeremy
> > > 
> > > On Mon, Aug 19, 2019 at 2:12 PM amber lauer <amberlauer at gmail.com> wrote:
> > > Hi Jeremy, it's actually pretty easy. 
> > > 
> > > Look in your inlist star_job section and note the name of the network.
> > > 
> > > The default version of this file is located in $MESA_DIR/data/net_data/nets/ .
> > > 
> > > Copy this file to your model folder. Then open it with a text editor. Unless you are using one of the hard coded nets (approx21*) you will see the format is pretty easy to understand, there will be either:
> > > 
> > > add_isos_and_reactions()
> > > 
> > > or
> > > 
> > > add_isos()
> > > 
> > > add_reactions()
> > > 
> > > (and possibly remove_reactions())
> > > 
> > > I think the format is pretty self explanatory. If you use add_isos_and_reactions, you need only list the isos and the code will add all reactions connecting them. The alternative is to do it by hand using add_isos and add_reactions separately. But if you get stuck come back to the list and we can help.
> > > 
> > > Just a note, whatever your network name, MESA will look in your local model folder for the file first. I recommend changing the name to something verbose (and changing the value in the inlist).
> > > 
> > > Good luck!
> > > 
> > > =================================
> > > Dr. Amber Lauer
> > > Postdoctoral Researcher
> > > Triangle Universities Nuclear Lab
> > > Duke University
> > > amber.lauer at tunl.duke.edu
> > > 
> > > 
> > > On Mon, Aug 19, 2019 at 10:48 AM Jeremy Sakstein <sakstein at sas.upenn.edu> wrote:
> > > Hi Everyone,
> > > 
> > > I would like to add a new particle species (with associated reactions) so that it contributes to the EOS and the density.
> > > 
> > > How do I go about doing this? Is there a hook?
> > > 
> > > Cheers,
> > > 
> > > Jeremy
> > > _______________________________________________
> > > mesa-users at lists.mesastar.org
> > > https://lists.mesastar.org/mailman/listinfo/mesa-users
> > > 
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> > > 
> > 
>