<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>
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