[mesa-users] Network types and other details

amber lauer alauer1 at lsu.edu
Sun Feb 5 18:59:01 EST 2017


Maybe we can talk about this tomorrow Frank ;)

On Feb 5, 2017 3:39 PM, "Frank Timmes" <fxt44 at mac.com> wrote:

> p.s. - happy to correct any typos you find or clarify any mysterious steps.
>
> fxt
>
>
>
> > On Feb 5, 2017, at 12:33 PM, Frank Timmes <fxt44 at mac.com> wrote:
> >
> >> The benefit is that you can get away with far fewer isotopes
> >
> > the disadvantage, unseen by most, is the network evolution equations
> > and their jacobian get significantly more complicated. no free lunch ;)
> >
> >>> Is there an additional resource I can refer to on the approx networks
> and compound reactions?
> >
> > attached is an unpublished pdf that reveals the sorcery behind
> equilibrium reactions.
> > these techniques are used in the hardwired reaction networks aprox* and
> friends.
> >
> > fxt
> >
> >
> >
> >
> >> On Feb 5, 2017, at 12:01 PM, Robert Farmer <rjfarmer at asu.edu> wrote:
> >>
> >>> So, assuming I had a model that started with a specific abundance
> profile, but I used a soft network that didn't include the same isotopes,
> the missing isotopes would not be treated. Would they retain their original
> absolute mass, or mass fraction?
> >>
> >> They will be changed according to the rules mesa has for changing the
> network, see section 6.2.2 in the mesa3 paper, also see the
> star/private/adjust_xyz.f90 set_new_abundances function, isotopes not in
> the new net will be removed, but other similar isotopes will be re-scaled
> to compensate. Where similar is splits things up into neutron, hydrogen,
> helium, carbon, nitrogen, oxygen and others. Isotopes not in the old but in
> the new network get added based on solar abundances.
> >>
> >>> Is there an additional resource I can refer to on the approx networks
> and compound reactions?
> >> Maybe try and read through whats happening in net/private/net_approx21_procs.inc
> which is where the approx network logic is, though it can be hard to follow.
> >>
> >> Rob
> >>
> >>
> >>
> >> On Sun, Feb 5, 2017 at 11:39 AM, amber lauer <alauer1 at lsu.edu> wrote:
> >> Thanks. I did check the logic of the code since I know it is preferred
> that we dig into it ourselves, unfortunately I still wasn't sure, although
> I was pretty sure.
> >>
> >> So, assuming I had a model that started with a specific abundance
> profile, but I used a soft network that didn't include the same isotopes,
> the missing isotopes would not be treated. Would they retain their original
> absolute mass, or mass fraction?
> >>
> >> Is there an additional resource I can refer to on the approx networks
> and compound reactions?
> >>
> >>
> >> On Feb 5, 2017 1:20 PM, "Robert Farmer" <rjfarmer at asu.edu> wrote:
> >> Hi
> >>
> >> 1) Yes, though you can also specify the reactions if you want to do it
> manually but just setting the isotopes is easier. There other soft nets
> than the mesa_, the better way to think of it anything that is not an
> approx net is a soft network
> >>
> >> 2) The basic idea is you go h->he->c12 then go up by adding alpha's
> following the alpha chain reactions. There are then special reactions for
> some equilibrium reactions to avoid evolving the intermediate isotope. The
> benefit is that you can get away with far fewer isotopes and reactions to
> evolve a star with than a corresponding soft net, less isotopes makes mesa
> faster. There is also special handling for the final fe56-> something so
> you don't have to follow all the heavy isotopes.
> >>
> >> 3) Yes
> >>
> >> 4) No, approx nets are handled separately to soft nets, the approx nets
> are literally hard coded (each reaction is individually written out) into
> mesa while the soft nets are flexible with the reactions.
> >>
> >> 5) auto_extend_net only changes the net if you are currently using one
> of the nets specified in h_he_net or co_net. You can check the logic in
> star/job/run_star_support.f90 function extend_net
> >>
> >> 6) auto_extend will only switch between those three networks, while the
> adaptive network may change all the isotopes, effectively making its own
> new network at each step
> >>
> >> Rob
> >>
> >> On Sun, Feb 5, 2017 at 10:01 AM, amber lauer <alauer1 at lsu.edu> wrote:
> >> I'm trying to understand some details of fixed networks, please tell me
> if my assumptions are correct;
> >>
> >> 1) Soft nets only specify a fixed list of isotopes, the code supplies
> any reactions that link them. Any isotope not listed in the net file is not
> treated. These nets are indicated by the name mesa_*.net where * is the
> number of species.
> >>
> >> 2) Approx nets utilize compound reactions, which assume an equilibrium
> of intermediate isotopes not explicitly included in the net, and therefore
> can treat reactions involving these even if they are not explicitly
> included.  These are indicated by the name approx_*.net. If this is
> correct, how is this different from a network that explicitly lists the
> intermediate species?
> >>
> >> 3) All others are standard fixed networks that treat only the isotopes
> and reactions explicitly listed.
> >>
> >> 4) Network files can be created that are a combination of other
> networks, listing them by name. Can these be a combination of types 1),
> 2),  and 3)?
> >>
> >> 5) The auto_extend_net feature, which is set true by default, will
> extend beyond basic.net to cno_ burn.net and then to approx_21. What if
> the  network is changed to something else, will it still look to the co_net
> and adv_net networks if the specified net is insufficient?
> >>
> >> 6) Auto_extend_net does not apply to adaptive networks (if this is
> false, what does it do?).
> >
> >
> >
> >
> >
> > [The attachment effective_reaction_rates.pdf has been manually removed]
>
>
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