<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<body>
<div style="font-family:sans-serif">
<span dir="ltr" style="margin-top:0; margin-bottom:0;">Hi Johnny,</span> <br> <br> <span dir="ltr" style="margin-top:0; margin-bottom:0;">This is quite interesting given my understanding is that the inspiral for equal mass Lorene ID is usually quite reasonable. Specifically your note regarding the 20% difference between ADM Angular momentum for quasi-equilibrium and that resulting from your PN estimate ID seems quite wrong. Maybe the Lorene ID is at a poor resolution?</span> <br> <br> <span dir="ltr" style="margin-top:0; margin-bottom:0;">I did a test with the FUKA BNS code for a 1.4-1.4 BNS using a polytope at 45km and the difference in the ADM Angular momentum between a coarse solution using quasi-equilibrium and 3.5PN estimates was < 1%.</span> <br> <br> <span dir="ltr" style="margin-top:0; margin-bottom:0;">Cheers,</span> <br> <span dir="ltr" style="margin-top:0; margin-bottom:0;">Samuel Tootle</span> <br> <span dir="ltr" style="margin-top:0; margin-bottom:0;">Goethe Universität Frankfurt </span> <br>
</div>
<div><br>
<div>
<p><strong>From: </strong>Zach Etienne <zachetie@gmail.com><br><strong>To: </strong>Bing-Jyun Tsao <johnny.tsao.880724@gmail.com><br><strong>CC: </strong>users@einsteintoolkit.org<br><strong>Date: </strong>Oct 5, 2022 21:02:01<br><strong>Subject: </strong>Re: [Users] Eccentricity in BNS evolution with Lorene<br></p>
</div>
<blockquote style="margin:0;border-left:3px solid #ccc; padding-left:10px">
<div dir="ltr">
Hi Johnny,
<div><br>
</div>
<div>
I noticed you set
</div>
<div>
ADMBase::initial_shift = "zero"<br>
</div>
<div>
so you eliminated one possible contributor to coordinate eccentricity (Lorene's initial shift condition results in significant eccentricity). Good choice.
</div>
<div><br>
</div>
<div>
I don't use GRHydro/ML_BSSN, so I cannot comment on your choices there. Generic advice:
</div>
<div>
* Resolution may be too low -- try higher resolution & see if your eccentricity reduces.
</div>
<div>
* Initial data is too close (Lorene assumes a helical Killing vector, which is violated more and more as the initial separation of the stars decreases)
</div>
<div>
* Check that you are properly tracking the NSs such that they are centered within high-resolution AMR boxes, and that the radius of the AMR boxes is at least 1.5x the radius of each NS. A movie visualizing the density of the stars in the orbital plane would be very very useful.
</div>
<div><br>
</div>
<div>
Hope this helps!
</div>
<div><br clear="all">
<div>
<div dir="ltr" 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 Wed, Oct 5, 2022 at 11:41 AM Bing-Jyun Tsao <<a href="mailto:johnny.tsao.880724@gmail.com" target="_blank">johnny.tsao.880724@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">
<div dir="ltr">
Dear Einstein Toolkit community,
<div><br>
</div>
<div>
I am Bing-Jyun (Johnny) Tsao, a graduate student at University of Texas at Austin. I am currently working on a project comparing our local version of BNS initial data (M. Clark, P. Laguna, 2016 Physical Review D 94 064058) with Lorene.
</div>
<div><br>
</div>
<div>
When using Lorene, I found that the trajectory of the stars is showing eccentricity (as shown in the plot below), and this occurred when I ran Lorene with equal-mass BNS with ADM mass = 1.4 Msun, and with the publicly available Lorene data on their website "G2_I14vs14_D4R33_45km", both of which have an initial separation of 45 km. I use VolumeIntegral_GRMHD to track the stars, and GRHydro + ML_BSSN to evolve. Additionally, I also found that the ADM angular momentum from Lorene is about 20% smaller than that from our code which uses post-Newtonian calculations.
</div>
<div><br>
</div>
<div>
My question is:
</div>
<div>
From my understanding, Lorene gives quasi-circular initial data. Thus, is it abnormal to see eccentricity, or is it a physical artifact, perhaps from tidal deformation, that always shows up when the stars are very close to each other?
</div>
<div><br>
</div>
<div>
Here I attached my parfile and the trajectory for a run using the Lorene publicly available data "G2_I14vs14_D4R33_45km".
</div>
<div><br>
</div>
<div>
Thanks in advance.
</div>
<div><br>
</div>
<div>
Best,
</div>
<div>
Johnny Tsao
</div><br>
</div> _______________________________________________<br> Users mailing list<br> <a href="mailto:Users@einsteintoolkit.org" target="_blank">Users@einsteintoolkit.org</a><br> <a href="http://lists.einsteintoolkit.org/mailman/listinfo/users" rel="noreferrer" target="_blank">http://lists.einsteintoolkit.org/mailman/listinfo/users</a><br>
</blockquote>
</div>
</blockquote>
</div>
</body>
</html>