Hello Mikael,
Interesting point. I can play with the initial setup a bit.
Where is eos state change initiated? I believe the collapse occurs because there is a sudden lowering of the pressure !?
Yes. The way this is achieved is essentially that one constructs a TOV solution with a particular EOS, which would make a stable star. One then *evolves* with a different EOS (and a step in between to fix the constraints by keeping the stress-energy tensor constant and adjusting eg HydroBase::rho and HydroBase::press to achieve this).
I'll poke around some ...
First thing to do would be to check the density plot (I hope I have one) that is in the GRHydro paper (Loeffler et al.).
Yours, Roland