<div dir="ltr">Hi Erik,<div> thanks a lot for the offer to help. I will try to have a look by myself first at the mathematica notebook.</div><div><br></div><div>Unless anybody else knows on what paper CCZ4 in McLachlan is based on. :-)</div><div><br></div><div>Cheers,</div><div>Bruno</div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Il giorno mer 1 giu 2022 alle ore 22:48 Erik Schnetter <<a href="mailto:schnetter@gmail.com">schnetter@gmail.com</a>> ha scritto:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Bruno<br>
<br>
Although I was probably around when the CCZ4 formulation was<br>
implemented, I don't recall.<br>
<br>
I usually resolve to archaeology, comparing the equations in the<br>
respective Mathematica scripts to equations found in publications. If<br>
no one else speaks up, I can assist with this – we'd set up a Zoom<br>
meeting, and I can show how to read (or modify!) the Mathematica<br>
script that implements these equations.<br>
<br>
-erik<br>
<br>
On Tue, May 31, 2022 at 6:21 AM Bruno Giacomazzo<br>
<<a href="mailto:bruno.giacomazzo@unimib.it" target="_blank">bruno.giacomazzo@unimib.it</a>> wrote:<br>
><br>
> 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.<br>
><br>
> In Alic et al 2013 (<a href="https://link.aps.org/doi/10.1103/PhysRevD.88.064049" rel="noreferrer" target="_blank">https://link.aps.org/doi/10.1103/PhysRevD.88.064049</a>) 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).<br>
><br>
> 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)?<br>
><br>
> We were able to find some example parameter files (for example the ones from the Parma group <a href="https://einstein.pr.infn.it/gravity/Research/BNS2015.html" rel="noreferrer" target="_blank">https://einstein.pr.infn.it/gravity/Research/BNS2015.html</a>) and we found that they used indeed k1 and k2 from Alic et al 2013:<br>
> ML_CCZ4::dampk1 = 0.05<br>
> ML_CCZ4::dampk2 = 0<br>
><br>
> We also saw that they added ML_CCZ4::ML_Theta to the Dissipation vars and set<br>
> ML_CCZ4::apply_dissipation = "never".<br>
> The other parameters look the same as when using BSSN.<br>
><br>
> 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.<br>
><br>
> Thanks,<br>
> Bruno<br>
><br>
> --<br>
><br>
> Prof. Bruno Giacomazzo<br>
> Department of Physics<br>
> University of Milano-Bicocca<br>
> Piazza della Scienza 3<br>
> 20126 Milano<br>
> Italy<br>
><br>
> email: <a href="mailto:bruno.giacomazzo@unimib.it" target="_blank">bruno.giacomazzo@unimib.it</a><br>
> phone: (+39) 02 6448 2321<br>
> web: <a href="http://www.brunogiacomazzo.org" rel="noreferrer" target="_blank">http://www.brunogiacomazzo.org</a><br>
><br>
> ----------------------------------------------------------------------<br>
> There are only 10 types of people in the world:<br>
> Those who understand binary, and those who don't<br>
> ----------------------------------------------------------------------<br>
><br>
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<br>
<br>
-- <br>
Erik Schnetter <<a href="mailto:schnetter@gmail.com" target="_blank">schnetter@gmail.com</a>><br>
<a href="http://www.perimeterinstitute.ca/personal/eschnetter/" rel="noreferrer" target="_blank">http://www.perimeterinstitute.ca/personal/eschnetter/</a><br>
</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><p><font color="#000000">Pr<font face="arial, sans-serif">of. Bruno Giacomazzo<br>Department of Physics<br>University of Milano-Bicocca<br></font></font><span style="color:rgb(0,0,0)"><font face="arial, sans-serif">Piazza della Scienza 3<br></font></span><span style="color:rgb(0,0,0)"><font face="arial, sans-serif">20126 Milano<br></font></span><span style="font-size:12.8px;color:rgb(0,0,0)">Italy</span></p><p><font color="#000000"><span style="font-size:12.8px">email: </span><span style="font-size:12.8px"><a href="mailto:bruno.giacomazzo@unimib.it" target="_blank">bruno.giacomazzo@unimib.it</a><br></span><span style="font-size:12.8px">phone: (+39) 02 6448 2321</span></font><br><font color="#000000"><span style="font-size:12.8px">web: </span></font><span style="color:rgb(0,0,0);font-size:12.8px"><a href="http://www.brunogiacomazzo.org/" style="font-size:12.8px" target="_blank">http://www.brunogiacomazzo.org</a></span></p><p><font color="#000000">----------------------------------------------------------------------<br><span style="font-size:12.8px">There are only 10 types of people in the world:<br></span><span style="font-size:12.8px">Those who understand binary, and those who don't<br></span><span style="font-size:12.8px">----------------------------------------------------------------------<br></span></font></p></div></div></div></div></div></div></div>