#1201: Incorrect dtshift in Exact with shift_add_{x,y,z} parameters ------------------------------------+--------------------------------------- Reporter: barry.wardell | Owner: Type: defect | Status: new Priority: major | Milestone: ET_2013_05 Component: EinsteinToolkit thorn | Version: Resolution: | Keywords: ------------------------------------+---------------------------------------

Comment (by eschnett):

This problem has existed for a long time. I would not make this a release goal.

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