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Description of files in this directory
======================================
$Header$
This file contains (typically) one file for each model, containing
a Fortran-callable subroutine to compute the 4-metric $g_{ab}$ and
inverse 4-metric $g^{ab}$:
subroutine Exact__model_name_coords(
$ x, y, z, t,
$ gdtt, gdtx, gdty, gdtz,
$ gdxx, gdyy, gdzz, gdxy, gdyz, gdzx,
$ gutt, gutx, guty, gutz,
$ guxx, guyy, guzz, guxy, guyz, guzx,
$ psi, Tmunu_flag)
CCTK_REAL x, y, z, t
CCTK_REAL gdtt, gdtx, gdty, gdtz,
$ gdxx, gdyy, gdzz, gdxy, gdyz, gdzx,
$ gutt, gutx, guty, gutz,
$ guxx, guyy, guzz, guxy, guyz, guzx
CCTK_REAL psi
LOGICAL Tmunu_flag
...
RETURN
END
psi is normally unused, but can be set by the subroutine to explicitly
specify the Cactus static conformal factor. At present only the
"Minkowski_gauge_wave" model does this
The subroutine should set Tmunu_flag to .true. if this model needs
to set the stress-energy tensor (i.e. if it's non-vacuum and/or it has
a cosmological constant, or .false. if it doesn't (i.e. if it's vacuum
and has no cosmological constant).
FIXME: Wouldn't it be cleaner to just compute $g_{ab}$,
and use a 4x4 matrix inversion to get the other one?
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