Users March 2020

users@lists.einsteintoolkit.org

16 participants
24 discussions

Einstein Toolkit Meeting Reminder
by users＠einsteintoolkit.org 11 Mar '20

11 Mar '20

Hello, Please consider joining the weekly Einstein Toolkit phone call at 9:00 am US central time on Thursdays. For details on how to connect and what agenda items are to be discussed, use the link below. https://docs.einsteintoolkit.org/et-docs/Main_Page#Weekly_Users_Call --The Maintainers

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Agenda for Thursday's Meeting
by users＠einsteintoolkit.org 09 Mar '20

09 Mar '20

Please update the Wiki with agenda items for Thursday's meeting. Thanks! https://docs.einsteintoolkit.org/et-docs/meeting_agenda --The Maintainers

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Determination of the final spin of the remnant of a binary neutron star merger
by Beyhan Karakaş 07 Mar '20

07 Mar '20

Dear to whom it may concern, I am interested in determining the spin of the remnant which are resulted from binary neutron star (initially are in irrotational configuration) merger . How could the method to determine the final spin differ (if it does) in case of remnant is a black hole or a neutron star. For the former case, I suppose QuasiLocalMeasures parameter "begin_qlm_calculations_after" along with AHFinderDirect parameter "find_after_individual" should be set to the time/iteration that the black hole formed. If this is not the case, please clarify how could it be determined? In addition, is there a way to find the evolution of the spin and orbital eccentricity of the binary? Best regards, Beyhan.

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Fwd: Modifications to TOV collapse simulation for scalar collapse
by Roland Haas 06 Mar '20

06 Mar '20

Justin Verde had trouble sending to the mailing list (his email server being flagged as a spam host by sorbs) and asked me to forward. Forwarded email text follows: Hello everyone, I was able to successfully run the TOV collapse and have attached some build notes and the par file I used to do so, for anyone interested. I've begun using the simulation as a basis for building a scalar field collapse simulation, and am perhaps getting lost in some of the competencies/communications between the different thorns in the job. I've attached a .pdf that shows my understanding of the dependencies and inheritances across thorns in the TOV collapse. My current way forward involves: 1. Remove EOS_OMNI dependencies 2. Rewrite TOVSolver as a new thorn (ScalarSolver) 3. Replace GRHydro with similar thorn of reduced capabilities (GRScalar) I'm wondering if anyone has any best practices (previously documented, or otherwise) to take into account when doing so, or if there are any warnings to heed before playing around with duplicating a thorn. My worry is that I'll spend weeks making a mistake that I could have avoided by asking for help beforehand. My specific questions are as follows: 1. Is removing all EOS_OMNI-related comments from the par file adequate? 2. In the TOVSolver documentation there is a reference to a "scalar field code" that uses the CalcTmunu interface, which seems to refer to a code doing similar things to what I'm trying to do. Is there somewhere I could get this code, or a simulation that may help see what hydro elements I can remove? 3. If I were to completely remove GRHydro, what functionalities would I lose? I plan to use it to handle the evolution equation for my scalar field by simply removing any strictly hydro (or shock) parts that don't seem necessary. Is this (in)advisable? Thanks again for all the community help I've received so far! -- Kindest Regards, Justin Verde

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meeting minutes for 2020-03-05
by Roland Haas 05 Mar '20

05 Mar '20

Present: Alois Peter Schaffarczyk, Bill, Chris, Helvi, Liu Haoyang, Justin Verde, Maria, Peter, Roland, Steve, Zach updates on codes: * Zach updated on status of Baikal. ** ready for review, Helvi is reviewer and informed, official "no harm is done" still outstanding, but do not expect problems. Hope to have go ahead tonight or tomorrow ** Zach conducted validation tests ** sped up code generation by adding parallelism ** documentation is currently in notebooks that are in nrpytutorial repository and not included in Baikal ** Roland suggested using a git submodule of nrpytutorial in Baikal to link it to the version used * Zach and Roland working on review ** code now incorporates piecewise polytropes ** code has documentation in notebook ** Roland to interact with Zach on how to generate and how to best compare * Steve updated PreSync and is now merged into mater ** by default is off and only enabled when setting parameters ** Found some failing thorns that Steve will interact with Zach on how to fix timeline of release: * call for volunteers for gallery examples * please encourage students since it is a good training for them to use the ET * open "major" tickets for the release: https://bitbucket.org/einsteintoolkit/tickets/issues?kind=bug&priority=majo… ET US release: * waiting for final graphics for website * will announce soon * still some travel funds left, please send email to Steve or via the registration form (once online) CarpetCode.org: * Erik has up to date git repo of website content * Ian created github hosted copy at: http://einsteintoolkit.github.io/carpetcode.org/ * needs update of DNS entry for carpetcode.org to point to it, not sure if this is already ongoing Unanswered questions: * http://lists.einsteintoolkit.org/pipermail/users/2020-March/007329.html which asks about spin of a neutron star. If one can wait long enough one could compute the ADM angular momentum at infinity. Pfeiffer et al. looked into computing spin of NS and (Roland recalls) ended up computing the qlm surface integral on a surface just above the NS surface * could also try and integrate the volumetric angular momentum which could be used (using the ADM-J volume integral) * for a BH + disk system one can try and combine the spin measured on the horizon (even if hairy) plus volume integral of spin in disk and combine to ADM spin * Zach will try to contact the person Open tickets: * https://bitbucket.org/einsteintoolkit/tickets/issues/2340/update-makethornl… * https://bitbucket.org/einsteintoolkit/tickets/issues/2337/ahfinderdirect-do… Workshop in Spain in July: * new frontiers in strong gravity * registration now open * http://benasque.org/2020relativity/ * some NSF funding and EU funds to support student travel, information on website Yours, Roland -- My email is as private as my paper mail. I therefore support encrypting and signing email messages. Get my PGP key from http://pgp.mit.edu .

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issue with Outflow after BHB merger
by Federico Cattorini 05 Mar '20

05 Mar '20

Dear all, I am having issues with the thorn Outflow running a BHB simulation with WhiskyMHD (parfile attached). Outflow correctly computes the flows on the single orbiting BHs during the inspiral, but after the merger it fails to compute it on the newly formed BH. I get the following warning in the .out: WARNING level 1 from host r149c18s02.marconi.cineca.it process 0 while executing schedule bin CCTK_ANALYSIS, routine Outflow::outflow in thorn Outflow, file /marconi/home/userexternal/fcattori/EinsteinToolkit/ET_2018_09/Cactus/arrangements/EinsteinAnalysis/Outflow/src/outflow.c:958: -> didn't find valid detector surface for sn=2, det=2 In my parfile I implement Outflow as outflow::compute_every = 64 outflow::num_detectors = 3 outflow::surface_index[0] = 0 outflow::surface_index[1] = 1 outflow::surface_index[2] = 2 outflow::interpolator_name = "Lagrange polynomial interpolation" outflow::interpolator_pars = "order=4" AHFinderDirect uses three spherical surfaces (n. 0,1,2). PunctureTracker tracks and write its values on n. 0 and 1. Does anyone know how to address this issue? Thanks a lot, Federico

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Einstein Toolkit Meeting Reminder
by users＠einsteintoolkit.org 04 Mar '20

04 Mar '20

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[USERS]CarpetInterp Problem while using with Multi-Refinement Levels
by Aryan Sharma 04 Mar '20

04 Mar '20

Hi all, This is a question about interpolation in Carpet. I am using InterpGridArrays in a function scheduled in CCTK_Initial for interpolating grid variables and, when I have a single refinement level (unigrid), the interpolation is done correctly with no error messages. When I have two refinement levels (level 0 and level 1), it happens that I need to use values of the variables at grid points on level 0 to interpolate to grid points on level 1. The points on level 0 I want to interpolate from are present on level 0 only. Refinement level 1 does not extend to that region. When I am running it with these 2 refinement levels, Cactus is giving me an error that some points are outside the grid (outside level 1). However, it should be possible for the InterpGridArrays function to interpolate the value at this point from the coarser refinement level as overall speaking the point is within the base grid of the simulation. Thus, My query is:-- Is there any way to schedule my routine in global mode so that InterpGridArrays can use values at grid points on level 0 while calculating interpolated values for grid points on refinement level 1? If I simply add OPTION: global or OPTIONS: global loop-local in my schedule.ccl file, the run crashes with a segmentation fault. Thank you for your time. I really hope you could look into it. Thanks and regards Aryan Sharma ᐧ

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Fwd: Assistant professor position at Lyon-1 University
by Bruno Giacomazzo 04 Mar '20

04 Mar '20

sorry if you already received this. ---------- Forwarded message --------- Da: Jerome <j.margueron(a)ipnl.in2p3.fr> Date: mer 4 mar 2020 alle ore 11:52 Subject: Assistant professor position at Lyon-1 University To: Jerome MARGUERON <margueron(a)ipnl.in2p3.fr> FYI, an assistant professor position (MCF) is now opened à Lyon-1 university on several subjects, including hydrodynamical simulations for GW (like NS mergers). Would you like to inform any possible candidate (French speaking is preferable)? The deadline to apply is March, 18th. Sincerely, Jérôme Margueron The Department of Physics of the Claude Bernard University Lyon invites applications for the following position as public employee starting on September 1st, 2020 with the beginning of the academic year. The position is a permanent position as assistant professor (Maitre de Conférence) of Claude Bernard University Lyon and the research can be held in the theory group of the 2-infinite physics Institute (IP2I). The incumbent should have a PhD in physics. While there is no age limit, this type of position are usually provided to early-career researcher. We are looking for candidates with an outstanding research record in some of the following fields: hydrodynamics, numerical relativity, MHD, gravitational-wave physics and its connections to neutron stars and nuclear physics. The position has a strong focus on hydrodynamic simulation in general relativity. Participation in current and future collaborative-research initiatives of the department of physics, as well as interdisciplinary cooperation within the faculty of sciences is expected. The ideal candidate has a PhD in theoretical physics and experience in teaching physics. The teaching part will be held in the department of physics, at the bachelor's degree level and at the master level. It is mandatory to have had a teaching experience (at least 100h) at the bachelor level to apply to this position and to be able to teach in french. It is strongly preferred if the candidate has obtained the CNU "qualification au métier d'enseignant-chercheur". If the candidate does not have the French qualification, he/she should shortly contact the director of the physics department for further details. The opening date is running from 17/02/2020 to 18/03/2020 (4pm CET). More details can be found here: https://www.galaxie.enseignementsup-recherche.gouv.fr/ensup/ListesPostesPub… and the procedure to candidate is explained on : https://www.galaxie.enseignementsup-recherche.gouv.fr/ensup/cand_postes_GAL… or directly here : https://galaxie.enseignementsup-recherche.gouv.fr/antares/can/astree/index.… For more information on the teaching profil candidate can contact : J.-C. Plenet, director of the physics department, jean-claude.plenet(a)univ-lyon1.fr, (+33) 4 72 43 11 96. For more information on the research profil candidate can contact : Anne Ealet, director of IP2I, a.ealet(a)ip2i.in2p3.fr, (+33) 4 72 44 84 57.

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Fw: Questions about the nsnstohmns.par
by Hamilton, Maria 04 Mar '20

04 Mar '20

From: Roland Haas <rhaas(a)illinois.edu> Sent: Tuesday, March 3, 2020 6:29 PM To: Hamilton, Maria Cc: Peter Diener Subject: Re: Questions about the nsnstohmns.par Hello Maria, > 1. The parameter has refinement levels, and regrid radius, but > does not have time_refinement_factors. Is this on purpose? Should it > be there? Without setting time_refinement_factors it uses the default which is a factor of 2 between each level. Many of the BBH parfiles use a factor of 1 between the coarsest level, however for NS this is often not required (the differing factor is only there to cure an instability in the shift condition). > 2. CarpetRegrid2 is given 3 num_centers, if first and second are > the NSs, what is the role of the third, why does it have only 1 > num_level, and why is not centered at 0? The third one is created without any boxes. I will contain the merged star / black hole once it forms. The Triger thorn (see your question 4) is used to enable refinement levels for this center once a horizon is about to form (lapse drops below a given value). Since it is only a placeholder initially it is set to 1 level and since it will capture the black hole that forms at the origin it is centered on the origin. > 3. CarpetRegrid2 is given position_x_1 and position_x_2, if those > are the centers for the NSs, why is 15.1875 for a 45 radius? If I > want the radius to be 50, how do I change this? 45 is in km. So 45km is ~30Msun distance which gives a radius of ~15Msun (Msun being the code unit as well). > 4. Why do I need Trigger? Trigger is needed to enable grid changes once a horizon is about to form. > 5. If I want to search for a BH as final result, how do I add > AHFinderDirect? Isn't it already there? If not then you can add it as usual but set eg the parameter "find_individual_after[n]" of the horizon to some huge value (1e6 or so) and have the Trigger thorn steer that value to "0." once it enables the central grid patch so that the horizonfinder starts looking for horizons (there may also be a more direct "enable" parameter listed in AHFinderDirect's param.ccl that you could use instead of hacking find_invidual_after, or whatever its name actually is. > 6. SphericalSurface is given 5 surface, but surface [2] is > skipped. Why? That one was likely intended / used for a black hole horizon. There is no reason for the set of used surfaces being contiguous really. > Thank you for your time, and I hope you won't mind my questions. No worries. As usual I would like to encourage these question to be asked on the users mailing list so that others can contribute (and benefit from the answers eventually). Yours, Roland -- My email is as private as my paper mail. I therefore support encrypting and signing email messages. Get my PGP key from http://pgp.mit.edu .

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