RotatingSymmetry90: abort when evaluating tensor type for Weyl scalars

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Issue #949 wontfix
Bruno Mundim created an issue

RotatingSymmetry90 is aborting when evaluating tensor type for Weyl scalars. It doesn't take into account the ManualCartesian type for example. The attached patch avoids that.

Keyword: RotatingSymmetry90

Comments (8)

  1. Bruno Mundim reporter
    • changed status to resolved
    • removed comment

    On a second thought, I should actually comment out the Weyl scalars from my parameter file, since it doesn't make any sense to measure them in spherical symmetry!

  2. Roland Haas
    • removed comment

    I am not quite sure if one does not have to be a bit more careful with ManualCartesian quantities. If I define Psi = x*y^2^ then this would have ManualCartesian parities of (-,+,+). If I understand RotatingSymmetry90 correctly it would copy the value psi(i=10,j=1,k=0) to point (i=-1,j=10,k=0). However the Psi I defined would have (among other changes) changed sign as x (or i) changes sign. So a simple copy would not seem to be correct.

    My understanding of RotatingSymmetry is limited and that of Weyl scalars very spotty at best. So don't take this objection too serious :-).

  3. Ian Hinder
    • removed comment

    The manual Cartesian parities specify the sign changes of the function under ''reflections'' in the planes perpendicular to the axes. These can therefore be used directly by ReflectonSymmetry. With RotatingSymmetry180, the symmetry operation is fortuitously equivalent to a reflection in the x direction composed with a reflection in the y direction, so if you know how a function transforms under reflections in the axes, you can determine how it transforms under the 180 degree rotation. RotatingSymmetry180 contains the logic to apply the parities that have been chosen. However, I don't think that a 90 degree rotation can be written as a composition of reflections, so the manual Cartesian parities are not useful here. In any case, RotatingSymmetry90 does not take account of these parities.

  4. Erik Schnetter
    • removed comment

    This patch only removes a check, it does not implement actually looking at these parities.

    It does make sense to look at them -- e.g. Psi_2 contains valuable information about mass and spin also in spherical symmetry.

  5. Tanja Bode
    • changed status to open
    • changed component to Cactus
    • removed comment

    This is a duplicate of #884, which I will now close as this thread has more content. While it may not be of use to you in your specific parameter file and project, this is not strictly invalid. WeylScal4 calculates Weyl scalars besides Psi4, which may be of interest to those studying systems for which RotatingSymmetry90 is applicable. Regardless, a symmetry thorn should support all tensortypealiases available. I am reopening, but downgrading to minor as I expect this won't be of interest to many and it does abort with a helpful error. I'll get around to it when I can.

  6. Bruno Mundim reporter
    • removed comment

    Thanks for pointing that out! I see that it has its value for the other Weyl scalars other than Psi4. Erik: thanks for pointing out the issue with the patch. I guess I rushed into it and didn't actually implement the correct solution. I will take a deeper look later and see if I can come up with a better patch.


  7. Roland Haas
    • edited description
    • changed status to wontfix

    ManualCartesian implies a single transformation behaviour for all variables in the group. However for RotatingSymmetry90 there needs to be something like an "x" and a "y" component of the tensor identifyable which ManualCartesian cannot provide.

    Potentially this could be made to work for "weylscalars_real" if the identity of the scalars in the group are known (they are in RotatingSymmetry). No ET thorn uses this however. Possibly PsiKadelia would have.

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