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HELP FOR: qload
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CALLING SEQUENCE: qload ( fileName ):
PARAMETERS: fileName - name of metric or basis file (without the
.mpl extension) to be loaded
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SYNOPSIS:
- Reads the metric or basis contained in the file indicated by fileName
with a .mpl extension.
- Files are read by directories specified in the global variable
grOptionqloadPath. These directories are searched in order. If the
file is not found in one of these directories, or the
grOptionqloadPath is not assigned, the directory specified by
grOptionMetricPath is searched.
- The metric or basis which is loaded becomes the default spacetime for
subsequent calculations.
- Metric files can be created using the makeg() command. A number of commonly
used spacetimes are included in the GRTensorII distribution. An online
collection is kept at http://astro.queensu.ca/~grtensor/.
- Older metric files do not have an entry specifying the spacetime
signature. If the global grOptionLLSC variable is set true, then
the following assumptions are made: if the spacetime is specified
by a four dimensional metric or general basis, then the signature
is set to +2; if the spacetime is specified by a set of basis vectors
satisfying an NP inner product, then the signature is set to -2.
These assumptions are overridden if the signature is explicitly
contained in the metric file. If the grOptionLLSC variable is set
false, then the signature is left unnassigned unless the signature
is explicitly given by the metric file. See ?groptions for a
description of the grOptionLLSC variable. To see the signature
of the current spacetime, use grdisplay(sig).
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EXAMPLES:
> grOptionMetricPath := 'c:/metrics':
c:/metrics
> qload ( schw ):
Default spacetime = schw
For the schw spacetime:
Coordinates
a
x = [ r, theta, phi, t ]
Line element
2
ds =
2
d r 2 2 2 2 2 2
--------- + r d theta + r sin(theta) d phi + (- 1 + 2 m/r) d t
1 - 2 m/r
The Classical Schwarzschild metric
> grcalc ( R(dn,dn) ):
> grdisplay ( R(dn,dn) ):
For the schw spacetime:
Covariant Ricci
R(dn,dn) = All components are zero
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SEE ALSO: grload, makeg, groptions.
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