QuasiLocalMeasures qlm_spin doesn't work for spins not aligned along the z axis
Issue #2160
wontfix
Einstein Toolkit version: ET_2018_02.
Parameter file: qc0-mclachlan.par in einsteinexamples with the additional parameter TwoPunctures::par_S_plus [0] = +0.3
Problem: The diagnostic qlm_spin[0] returns a spin of 0, whereas the expected one should be 0.3.
If instead of TwoPunctures::par_S_plus [1] = +0.3 one sets
TwoPunctures::par_S_plus [2] = +0.3, qlm_spin[0] is correctly
outputting 0.3
This happens because QuasiLocalMeasures finds in both cases the rotational Killing vector d/dphi (as seen setting QuasiLocalMeasures::veryverbose = yes), which is correct in the second case (when the axis aligned with the z-direction), but doesn't sound right when the rotation is with respect to the x-axis.
Changing QuasiLocalMeasures::killing_vector_method to axial or gradient does not change the outcome.
Best regards, Gabriele
Keyword: QuasiLocalMeasures
Comments (2)
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- edited description
- changed status to wontfix
Works as designed. This limit should be documented.
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A similar question was asked on the mailing list and responded to in http://lists.einsteintoolkit.org/pipermail/users/2021-April/007931.html with:
so the Killing vector method was only ever designed to work with spins more or less along the z-direction and changing the method to compute the Killing vector will not help.