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 <[email protected]> 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 > [email protected] > http://lists.einsteintoolkit.org/mailman/listinfo/users > -- Erik Schnetter <[email protected]> http://www.perimeterinstitute.ca/personal/eschnetter/ _______________________________________________ Users mailing list [email protected] http://lists.einsteintoolkit.org/mailman/listinfo/users
