Hi all, The CCZ4 code was written initially by Dana Alic. Erik (and others) subsequently made improvements since then. As far as I know, it should be effectively implementing the equations as in gr-qc:1106.2254.
With regards to the k3 parameter, Dana previously had this to say: "[GammaShift] should actually be 'real' and its default value set to 0.5, as it corresponds to the k3 parameter in the CCZ4 paper ( http://arxiv.org/pdf/1106.2254.pdf). This is important, because it leads to fast instabilities if it is set to 1 and coupled with non-zero values of the damping terms." I hope this helps, Barry On Thu, 2 Jun 2022 at 16:02, Michael Muller <[email protected]> wrote: > Hi Bruno, > > I have gone through the notebook in the past and from what I could see, > the version of paper I (10.1103/PhysRevD.85.064040) > is implemented in the code, kappa_3 is encoded in the parameter ' > ML_CCZ4::GammaShift', and the changes for the > scaling of kappa_1 and kappa_2 with the lapse (eq. 27 and 28 in paper II, > 2013) are not implemented. > > I hope this helps. > Best, > Michael Müller > ------------------------------ > *From:* [email protected] < > [email protected]> on behalf of Bruno Giacomazzo < > [email protected]> > *Sent:* Thursday, June 2, 2022 10:04 AM > *To:* Erik Schnetter <[email protected]> > *Cc:* Einstein Toolkit Users <[email protected]>; Paolo > Garimberti <[email protected]> > *Subject:* Re: [Users] question about ML_CCZ4 parameters > > > CAUTION: This email originated from outside of the University of Guelph. > Do not click links or open attachments unless you recognize the sender and > know the content is safe. If in doubt, forward suspicious emails to > [email protected] > > Hi Erik, > thanks a lot for the offer to help. I will try to have a look by myself > first at the mathematica notebook. > > Unless anybody else knows on what paper CCZ4 in McLachlan is based on. :-) > > Cheers, > Bruno > > > Il giorno mer 1 giu 2022 alle ore 22:48 Erik Schnetter < > [email protected]> ha scritto: > > 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 > <[email protected]> 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: [email protected] > > 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 > > ---------------------------------------------------------------------- > > > > _______________________________________________ > > Users mailing list > > [email protected] > > http://lists.einsteintoolkit.org/mailman/listinfo/users > > > > -- > Erik Schnetter <[email protected]> > http://www.perimeterinstitute.ca/personal/eschnetter/ > > > > -- > > Prof. Bruno Giacomazzo > Department of Physics > University of Milano-Bicocca > Piazza della Scienza 3 > 20126 Milano > Italy > > email: [email protected] > 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 > ---------------------------------------------------------------------- > _______________________________________________ > Users mailing list > [email protected] > http://lists.einsteintoolkit.org/mailman/listinfo/users >
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