Bruno
Although I was probably around when the CCZ4 formulation was
implemented, I don't recall.
I usually resolve to archaeology, comparing the equations in the
respective Mathematica scripts to equations found in publications. If
no one else speaks up, I can assist with this – we'd set up a Zoom
meeting, and I can show how to read (or modify!) the Mathematica
script that implements these equations.
-erik
On Tue, May 31, 2022 at 6:21 AM Bruno Giacomazzo
wrote:
>
> Together with a student of mine we are trying to use the CCZ4 formulation
> implemented in McLachlan. We saw that most parameters are the same as in
> BSSN, but there are damping factors that need to be selected.
>
> In Alic et al 2013 (https://link.aps.org/doi/10.1103/PhysRevD.88.064049) they
> mention 3 damping factors (k1, k2, and k3), but in the param.ccl of
> McLachlan/ML_CCZ4 only k1 and k2 are mentioned (assuming they are the same).
>
> Is it because k3 is hardcoded to the value suggested in Alic et al 2013? Or
> does McLachlan/ML_CCZ4 use a different set of evolution equations (in which
> case, is there a reference)?
>
> We were able to find some example parameter files (for example the ones from
> the Parma group https://einstein.pr.infn.it/gravity/Research/BNS2015.html)
> and we found that they used indeed k1 and k2 from Alic et al 2013:
> ML_CCZ4::dampk1 = 0.05
> ML_CCZ4::dampk2 = 0
>
> We also saw that they added ML_CCZ4::ML_Theta to the Dissipation vars and set
> ML_CCZ4::apply_dissipation = "never".
> The other parameters look the same as when using BSSN.
>
> Since I never used ML_CCZ4 I want to be sure that I'm setting the parameters
> correctly and the damping factors seem to be the most delicate point.
>
> Thanks,
> Bruno
>
> --
>
> Prof. Bruno Giacomazzo
> Department of Physics
> University of Milano-Bicocca
> Piazza della Scienza 3
> 20126 Milano
> Italy
>
> email: bruno.giacoma...@unimib.it
> phone: (+39) 02 6448 2321
> web: http://www.brunogiacomazzo.org
>
> --
> There are only 10 types of people in the world:
> Those who understand binary, and those who don't
> --
>
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--
Erik Schnetter
http://www.perimeterinstitute.ca/personal/eschnetter/
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