[ET Trac] [Einstein Toolkit] #2160: QuasiLocalMeasures qlm_spin doesn't work for spins not aligned along the z axis

Einstein Toolkit trac-noreply at einsteintoolkit.org
Sat Jun 23 18:41:02 CDT 2018


#2160: QuasiLocalMeasures qlm_spin doesn't work for spins not aligned along the z
axis
---------------------------------+-----------------------------------
 Reporter:  sbozzolator@…        |       Type:  defect
   Status:  new                  |   Priority:  unset
Milestone:                       |  Component:  EinsteinToolkit thorn
  Version:  development version  |   Keywords:  QuasiLocalMeasures
---------------------------------+-----------------------------------
 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

-- 
Ticket URL: <https://trac.einsteintoolkit.org/ticket/2160>
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