[ET Trac] [Einstein Toolkit] #1201: Incorrect dtshift in Exact with shift_add_{x, y, z} parameters

[Einstein Toolkit]

#1201: Incorrect dtshift in Exact with shift_add_{x,y,z} parameters
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  Reporter:  barry.wardell          |       Owner:     
      Type:  defect                 |      Status:  new
  Priority:  major                  |   Milestone:     
 Component:  EinsteinToolkit thorn  |     Version:     
Resolution:                         |    Keywords:     
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Description changed by rhaas:

Old description:

> The Exact thorn has shift_add_{x,y,z} parameters for adding a constant to
> the shift. Considering these as a coordinate transformation using a
> vector v^i = [shift_add_x, shift_add_y, shift_add_z], such a
> transformation should affect both the shift and its time derivative. This
> is because the time derivative in the new coordinates differs from the
> time derivative in the old coordinates by a term v^j d(beta^i)/dx^j. This
> is correctly implemented as a 4D coordinate transformation in the
> EinsteinExact thorns and I have verified that the difference relative to
> the Exact thorn is given by this missing term.

New description:

 The Exact thorn has {{{shift_add_{x,y,z}}}} parameters for adding a
 constant to the shift. Considering these as a coordinate transformation
 using a vector {{{v^i = [shift_add_x, shift_add_y, shift_add_z]}}}, such a
 transformation should affect both the shift and its time derivative. This
 is because the time derivative in the new coordinates differs from the
 time derivative in the old coordinates by a term {{{v^j d(beta^i)/dx^j}}}.
 This is correctly implemented as a 4D coordinate transformation in the
 EinsteinExact thorns and I have verified that the difference relative to
 the Exact thorn is given by this missing term.

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Ticket URL: <https://trac.einsteintoolkit.org/ticket/1201#comment:4>
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