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Cactus Code Thorn RotatingSymmetry90
Author(s) : Erik Schnetter <schnetter@cct.lsu.edu>
Maintainer(s): Erik Schnetter <schnetter@cct.lsu.edu>
Licence : GPL
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1. Purpose
Provide a 90 degree rotational symmetry boundary condition. This is
the kind of symmetry that exists e.g. in a single black hole evolution
when the black hole has spin. The same setup also admits an
additional bitant symmetry.
Currently the symmetry is fixed to be located at the lower x and y
boundaries, so that there is a rotation about the z axis.
The coordinate thorn does not know about this symmetry. You will have
to set up the domain such that you have an upper quadrant in the x and
y directions.
This symmetry boundary condition can be mixed with arbitrary symmetry
conditions in the z direction, e.g. bitant or periodicity.
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R90: operator that rotates points (counter-clockwise) by 90 degrees
f(x) = f(R90 x) = f(R180 x) = f(R270 )
symmetry about x=0:
f (-x) = f (+x)
vx (-x) = vx (+x)
vy (-x) = -vy (+x)
vz: same as scalar
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