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Vector_systems ['file1'] 'file2' ['file3'] [-n] [-i] [-t=n] [-v] [-C] [-H] [-F] [-S]file1: matrix_TYP containing a presentation of the group (cf. Presentation)
-n: only calculates the number of extensions, without computing
representatives. This option is much faster for big cohomology
groups. WARNING: Try this option first for 2-groups in dimension
greater than 4.
-v: verbose mode. Give some echoing to stderr to
indicate a little what the program is doing.
-i: Identify the cozycles given in file3, ie. give
the described space groups a name. CAUTION: The
name will depend on the generating set of the group
in file2 and the presentation in file1.
Can be used to test isomorphism of space groups with equal
point groups. The name is 0 iff the extension splits.
-t=n: Has an effect only if given with -i. Outputs the
isomophism needed to transform the space group
By default, only the linear part is calculated. To
get a full transformation matrix, use -t=2.
-C: Ignore the operation of the normalizer, just work
on the level of extensions.
-H: echo the isomorphism type of the cohomology group
H^1(G,Q^n/Z^n) to stderr.
-F: Only construct those extensions which gie rise to
torsion free space groups. Does not work in conjunction
with -n.
-S: write corresponding space groups in files
THE PROGRAM RELIES HEAVILY ON THE FOLLOWING TWO FACTS:
See also for Extract, Presentation, Same_generators and Zass_main.
'file1' can be left out, but the program is faster, if the presentation is given.
Vector_systems is a synonym for Extensions.
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