[Mesa-users] Adding a new particle species

[Jeremy Sakstein]

Thanks Frank. I was actually interested in the pair production process
where a photon pair produces electron positron pairs, the one that causes
the instability in massive stars.

On Mon, Aug 19, 2019 at 10:21 PM Francis Timmes <fxt44 at mac.com> wrote:

> 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
> > > >
> > > > _______________________________________________
> > > > mesa-users at lists.mesastar.org
> > > > https://lists.mesastar.org/mailman/listinfo/mesa-users
> > > >
> > >
> >
>
>
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