[Users] BHNS simulation issues - Hamiltonian constraint violations and general problems

Samuel Tootle tootle at itp.uni-frankfurt.de
Sat Aug 21 16:03:36 CDT 2021

Hi Konrad,

Have you checked the import of the ID from the hydro point of view (i.e. plot rho in for the first iterations). If you see drastic changes in the NS density in the initial iterations, it usually means the EOS manager isn't configured correctly which routinely results in the NS "vanishing" thereby destroying the solution and the evolution.


*From: *Konrad Topolski <k.topolski2 at student.uw.edu.pl>
*To: *Einstein Toolkit Users <users at einsteintoolkit.org>
*Date: *Aug 21, 2021 22:30:57
*Subject: *[Users] BHNS simulation issues - Hamiltonian constraint violations and general problems

> Hi all
> I am trying to run a BH-NS simulation using at least one of some (and sometimes more) unofficial thors.
> That would be Kadath for the initial data and possibly THC for hydro evolution.
> I'm trying to run the simulation either with GRHydro or with THC.
> In both cases I believe that the initial data gets imported correctly - I have looked at some simple visuals which I'm attaching to this mail.
> However, as the simulation proceeds, huge hamiltonian constraint violations occur and e.x. the lapse gets driven to 0 globally. This can also be seen.
> How can I help this? Is it because the puncture is not tracked correctly? Trying to set up a PunctureTracker at the location of the black hole yields a failure very soon, as the shift at puncture is said to be (nan, nan, nan).
> I'm sending the .par files, outputs (.out), errors (.err) and visualization (.png).
> Best regards
> Konrad
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