Hello Zach, > I generally suggest shifting the grid so that the closest gridpoint > to the origin is (dx/2, dy/2, dz/2), where dx,dy,dz are the > resolutions on the finest grid. I've used this trick many times to > stabilize evolutions. Also you may want to try the ShiftedKerrSchild > thorn (in the ETK), which enables a radial offset that shrinks the BH > coordinate size but at the same time kills off enormous constraint > violations near r=0. Unlike the existing KerrSchild thorn(s), this > one uses the standard Kerr-Schild metric written in spherical > coordinates and does the basis xform. Right, I had completely forgotten about that one. Thank you. So ShifterKerrSchild is actually different from Exact with its Kerr_KerrSchild__epsilon parameter (ie it would do proper coordinate transformation r -> r+r0 rather than just add r0 in some of the 1/r terms)?
Note that the goal is use it only as ID and not to reset the metric at each time so I will have to modify ShifterKerrSchild a bit. Yours, Roland -- My email is as private as my paper mail. I therefore support encrypting and signing email messages. Get my PGP key from http://pgp.mit.edu .
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