<div dir="ltr">Dear Mario,<div><br></div><div>> Thank you for your prompt reply. We are interested in the Einstein Toolkit tools, particularly in the AHFinderDirect tool, and we installed it already on our devices following the tutorial on the website "<a href="https://einsteintoolkit.org/" target="_blank">https://einsteintoolkit.org/</a>". It is a very powerful tool.</div><div><br></div><div>Yes, sorry one important detail may not have been very clear in my original email: The software I pointed to converts the Einstein Toolkit to a library that any numerical relativity code can interact with. In fact the example included in the software sets up a spinning black hole in a NRPy+-based code (which has a different infrastructure than the Einstein Toolkit), and then calls the Einstein Toolkit library to perform apparent horizon diagnostics. AHFinderDirect is used for these diagnostics.</div><div><br></div><div>Alternatively, you could "simply" write an Einstein Toolkit module (we call a module a "thorn") that reads in the data from your code onto an Einstein toolkit grid, then performs the horizon diagnostic. An unformatted data file could be used for this, so long as your Einstein Toolkit module knows the format of the data.</div><div><br></div><div>Regardless of the technique used, AHFinderDirect needs as input both the ADM 3-metric gamma_{ij} and extrinsic curvature K_{ij} in Cartesian coordinates.</div><div><br></div><div>Anyway, hope this helps!</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 Sat, Sep 24, 2022 at 3:31 AM Mario Imbrogno <<a href="mailto:mario.imbrogno97@gmail.com">mario.imbrogno97@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"><div>Dear Prof. Zach Etienne,</div><div><br></div><div>Thank you for your prompt reply. We are interested in the Einstein Toolkit tools, particularly in the AHFinderDirect tool, and we installed it already on our devices following the tutorial on the website "<a href="https://einsteintoolkit.org/" target="_blank">https://einsteintoolkit.org/</a>". It is a very powerful tool.</div><div><br></div><div>Finding Apparent Horizons (AHs) becomes necessary since we have an article under review, and one of the Referees asked us to compute the AHs on initial data because he was not convinced that the simulated black holes were actually three separate objects, at least initially. To do this, we had considered embedding new modules into our full-GR code, but, since these should be tested before being used (as you know the procedure for the finding of such surfaces is not trivial at all), we thought it was appropriate to rely on some other well-tested codes, perhaps the Einstein Toolkit, which we will cite in our paper.</div><div><br></div><div>So, we thank you for the tips you have given us and we would like to ask you if this is all or if there are some other details we need to be aware of. For example, our BSSN fields (among which there are the initial 3-metric and the extrinsic curvature) are stored in an "UNFORMATTED" data file, so could any problems arise about this? At the most, we have to convert our data to another format, do we not?</div><div><br></div><div>Best regards,</div><div><br></div><div>Mario Imbrogno<br></div><div><br></div><div><br></div><div><br></div><div> <br></div><div><br></div><div><br></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Il giorno ven 23 set 2022 alle ore 17:54 Zach Etienne <<a href="mailto:zachetie@gmail.com" target="_blank">zachetie@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"><div dir="ltr">Dear Mario,<div><br></div><div>With the help of fellow Einstein Toolkit Maintainer Roland Haas, I wrote a library for reading in Cartesian grid data to AHFinderDirect and QuasiLocalMeasures (additional, isolated horizon diagnostics) from any numerical relativity code. The code is open source, and has been used to analyze horizons from spacetime data generated by NRPy+.</div><div><br></div><div>Here's how you get it:</div><div><br></div><div>git clone <a href="https://bitbucket.org/zach_etienne/et_minimal_2019_03.git" target="_blank">https://bitbucket.org/zach_etienne/et_minimal_2019_03.git</a><br></div><div>cd et_minimal_2019_03</div><div>git checkout remotes/origin/with_quasilocalmeasures</div><div><br></div><div>Check out the README.md</div><div><br></div><div><span style="font-size:12.8px">-Zach</span><br></div><div><div><div dir="ltr"><div dir="ltr"><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"><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><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Sep 23, 2022 at 6:36 AM Mario Imbrogno <<a href="mailto:mario.imbrogno97@gmail.com" target="_blank">mario.imbrogno97@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="auto"><div dir="auto">Dear Einstein-Toolkit community, </div><div dir="auto"><br></div><div dir="auto">my name is Mario Imbrogno and I am a Ph.D. student at </div><div dir="auto">the University of Calabria (UniCal, Cosenza, Italy) under the supervision of prof. Sergio Servidio.</div><div dir="auto"><br></div><div dir="auto">Our research group had developed a spectral code to solve the Einstein equations via a</div><div dir="auto">pseudo-spectral technique [Meringolo C, Servidio S, and Veltri P "A spectral method algorithm for numerical </div><div dir="auto">simulations of gravitational fields." Classical and Quantum Gravity 38.7 (2021): 075027], and I am studying different cases of merging two and more </div><div dir="auto">black holes, in vacuum conditions.</div><div dir="auto"><br></div><div dir="auto">Now I have to compute the apparent horizons (AHs) just for our initial conditions, and I have</div><div dir="auto">read that the Einstein Toolkit implements the AHFinderDirect, a code that can detect the AHs.</div><div dir="auto"><br></div><div dir="auto">My questions are: is there a way to compute such AHs by, just uploading our 3D cartesian BSSN fields and </div><div dir="auto">using the AHFinderDirect code? </div><div dir="auto"><br></div><div dir="auto">Who is(are) the user(s) that mainly use(s) such code? Who can I ask?</div><div dir="auto"><br></div><div dir="auto">Where can I find a detailed guide in which I can learn how to upload my data using the AHFinderDirect code?</div><div dir="auto"><br></div><div dir="auto">If someone will help us, there is no problem for us to include as a co-author of our paper.</div><div dir="auto"><br></div><div dir="auto">Best regards,</div><div dir="auto"><br></div><div dir="auto">Mario Imbrogno</div></div>
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