Hi Stefan,

We certainly hope the Einstein Toolkit will be useful for you.

On Mon, 13 Jan 2014, sruehe@astrophysik.uni-kiel.de wrote:

Hallo Einsteintoolkit-Community,

i'm a phd-student in my first year at University zu Kiel, Germany. I've read many papers and saw the Toolkit for simulating relativistic hydrodynamics at black holes. First i have some important qustions and hope you can help me.

Does the BSSN-algorithm regard the hydrodynamic mass as source function in the current timestep to calculate the hypersurface of the next timestep?

Yes. The spacetime evolution equations includes the source terms coming from the stress-energy tensor of the matter. Thus the spacetime evolution does take into account the matter content.

Does this work via the TmunuBase?

Yes. The stress-energy tensor is set by the hydrodynamics thorn (GRHydro) in TmunuBase and read by McLachlan (implementing the BSSN equations) when needed.

Is the self-gravitation of the hydrodynamics calculated by the perturbation of the spacetime?

No, there is no perturbations involved. As the spacetime is evolved with the matter sources and GRHydro uses the full metric (through ADMBase) the code can perform a fully consistent and fully relativistic simulation of both spacetime and matter.

It is also possible to turn of the spacetime evolution and just perform a hydro evolution on a fixed spacetime.

I hope you can help me, thank you very much.

I hope this answers your questions,

Stefan Ruehe

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Cheers,

Peter