Hi All,
I've been trying to use the ADMMass thorn to calculate the ADM mass for a binary black hole system. The initial ADM mass given by TwoPunctures is 0.989, but ADMMass returns 0.031 (using both of the available methods).
Does anyone know what could be going wrong? Alternatively, are there other thorns that can be used to calculate the ADM mass?
Thanks in advance!
Gwyneth
Gwyneth
You can use the thorn QuasiLocalMeasures, and apply it to a large surface (that is obviously not a horizon), but still a bit away from the outer boundary. Many quantities calculated by QuasiLocalMeasures make sense away from the horizon. I recommend looking at e.g. the Hawking mass there. The Hawking mass (and other quasi-local mass definitions) are generalisations of the ADM mass that also make sense at finite differences. In general, they have lower errors than the ADM mass formula itself when calculated at a finite difference; the ADM mass has errors proportional to 1/r when evaluated at a finite radius.
The example parameter file "qlm-ce-ks-boosted.par" might help you get started. If you are interested in pursuing this, please ask on the mailing list or on our Slack channel, or on our weekly phone calls. (I'll be travelling tomorrow morning and will miss that call.)
-erik
On Sun, Jan 29, 2017 at 5:41 AM, Gwyneth Allwright allgwy001@myuct.ac.za wrote:
Hi All,
I've been trying to use the ADMMass thorn to calculate the ADM mass for a binary black hole system. The initial ADM mass given by TwoPunctures is 0.989, but ADMMass returns 0.031 (using both of the available methods).
Does anyone know what could be going wrong? Alternatively, are there other thorns that can be used to calculate the ADM mass?
Thanks in advance!
Gwyneth
Users mailing list Users@einsteintoolkit.org http://lists.einsteintoolkit.org/mailman/listinfo/users
On Sun, Jan 29, 2017 at 12:41:20PM +0200, Gwyneth Allwright wrote:
Hi All,
I've been trying to use the ADMMass thorn to calculate the ADM mass for a binary black hole system. The initial ADM mass given by TwoPunctures is 0.989, but ADMMass returns 0.031 (using both of the available methods).
Does anyone know what could be going wrong? Alternatively, are there other thorns that can be used to calculate the ADM mass?
The ADMMass thorn calculates the ADMMass by the spacetime, but not including punctures. The best way to go about that is to exclude the BH interior from the ADMMass calculation (there are already parameters for that), and to add the BH mass returned by the AHFinder (AHFinderDirect) to that for a total mass.
Frank
Hi Erik and Frank,
Thank you very much for clearing up my confusion! I will try using both QuasiLocalMeasures and the ADMMass/AHFinderDirect combination.
All the best,
Gwyneth
On Sun, Jan 29, 2017 at 7:37 PM, Frank Loeffler knarf@cct.lsu.edu wrote:
On Sun, Jan 29, 2017 at 12:41:20PM +0200, Gwyneth Allwright wrote:
Hi All,
I've been trying to use the ADMMass thorn to calculate the ADM mass for a binary black hole system. The initial ADM mass given by TwoPunctures is 0.989, but ADMMass returns 0.031 (using both of the available methods).
Does anyone know what could be going wrong? Alternatively, are there other thorns that can be used to calculate the ADM mass?
The ADMMass thorn calculates the ADMMass by the spacetime, but not including punctures. The best way to go about that is to exclude the BH interior from the ADMMass calculation (there are already parameters for that), and to add the BH mass returned by the AHFinder (AHFinderDirect) to that for a total mass.
Frank
users@lists.einsteintoolkit.org
-
Erik Schnetter -
Frank Loeffler -
Gwyneth Allwright