<div dir="ltr">Hi Deborah,<div><br></div><div>I'd be curious to see a comparison between the junk radiation you're seeing now versus before, for the same physical scenario, grids, etc. Also, the extra wiggles/reflections are typically caused not by junk radiation but by a sharp gauge feature (<a href="https://arxiv.org/abs/1404.6523">https://arxiv.org/abs/1404.6523</a>). The two can be easily distinguished as the former propagates at c, and the latter at sqrt(2) c (see paper for details).</div><div><br clear="all"><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div style="font-size:12.8px">-Zach</div><div style="font-size:12.8px"><br></div><span style="font-size:12.8px">* * *</span><br style="font-size:12.8px"><span style="font-size:12.8px">Zachariah Etienne</span></div><div><span style="font-size:12.8px">Assoc. Prof. of Physics, U. of Idaho</span></div><div><span style="font-size:12.8px">Adjunct Assoc. Prof. of Physics & Astronomy, West Virginia U.</span></div><div dir="ltr"><div><a href="https://etienneresearch.com" target="_blank">https://etienneresearch.com</a></div><div><a href="https://blackholesathome.net/" target="_blank">https://blackholesathome.net</a><br></div></div></div></div></div></div></div></div></div></div></div></div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Aug 9, 2022 at 4:41 PM Erik Schnetter <<a href="mailto:schnetter@gmail.com">schnetter@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Deborah<br>
<br>
One one hand, TwoPunctures has parameters to choose the resolution of<br>
the spectral grid it uses. I assume you are aware of these, and that<br>
you also know how to choose the 3D AMR grid setup parameters.<br>
<br>
TwoPunctures only solves for the conformal factor. It does per se not<br>
directly choose a lapse and a shift, but their choice is important in<br>
practice. Choosing \alpha=1 and \beta^i=0 as initial conditions is<br>
often not good. Similarly, choosing the antisymmetry lapse (with<br>
\alpha=-1 at the puncture) is also a bad idea (it is ill-posed). The<br>
TwoPunctures toolkit in the Einstein Toolkit has several options for<br>
choosing the initial gauge conditions. Personally, I am partial to<br>
initial_lapse = "twopunctures-averaged", but I am sure that others<br>
have other preferences.<br>
<br>
Of course, the BSSN gauge parameters used during evolution will also<br>
play a role.<br>
<br>
You can look at the gallery example at<br>
<<a href="http://einsteintoolkit.org/gallery/bbh/index.html" rel="noreferrer" target="_blank">http://einsteintoolkit.org/gallery/bbh/index.html</a>> for ideas.<br>
<br>
-erik<br>
<br>
<br>
<br>
On Tue, Aug 9, 2022 at 4:47 PM Ferguson, Deborah<br>
<<a href="mailto:deborah.ferguson@austin.utexas.edu" target="_blank">deborah.ferguson@austin.utexas.edu</a>> wrote:<br>
><br>
> Hi,<br>
><br>
><br>
><br>
> We had been using our own version of TwoPunctures, and I’ve recently switched to the ETK version since it doesn’t require solving for the masses separately. Junk radiation has always been present, but I’m finding that some of my recent simulations have particularly loud junk radiation, which also makes it harder avoid reflection of. So I’m guessing I’m not fully understanding the TwoPunctures parameters.<br>
><br>
><br>
><br>
> I’ve attached a parfile and a psi4 plot for a simulation I’ve started that’s having this large junk radiation, and was hoping someone could point out any mistakes I may have in the TwoPunctures parameters.<br>
><br>
><br>
><br>
> Thanks!<br>
><br>
> Deborah<br>
><br>
><br>
><br>
> --------------------------------------<br>
><br>
> Deborah Ferguson<br>
><br>
> Post Doc<br>
><br>
> University of Texas at Austin<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>
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</blockquote></div>