On Mon, Mar 27, 2017 at 11:12:26AM -0500, Peter Diener wrote:
To perform simulations a lot of infrastructure (a la what is available in SpEC) to control the shape and size of the horizons during a dynamical evolution.
Also maybe adding to this: In matter simulations one also often ends up with at least one black hole, even a moving black hole. In those cases it seems "good enough" to apply a little more dissipation well within the horizon to not crash - and that is really all you need. Nothing bad seems to "come out" of the black hole. You simply evolve everywhere and "ignore" what is going on well "inside the BH".
I didn't test this for a binary black hole system, but I wouldn't see why this shouldn't work as well. I don't think excision is really needed; but that of course also depends on how you evolve the space time. Punctures used to be evolved differently, when their nature was exploited to get rid of some of the singular behavior, but that is isn't used anymore, at least not in the Einstein Toolkit afaik, not even for binary black holes.
So I guess as short answer: you cannot use excision and Mclachlan in the Einstein Toolkit, but you should not need to for binary black holes.
Frank