I have made available a new GAP4 prepackage, Carat, and an update
of the prepackage CrystGap. Both are available for download under
The Carat prepackage is a set of GAP4 interface routines to a
collection of stand-alone programs, also called Carat. These
stand-alone programs, developed in the group of Prof. W. Plesken,
RWTH Aachen, allow to perform various computations with
crystallographic groups, notably the computation of normalizers
in GLnZ, and conjugators in GLnZ, and Bravais groups. Carat thus
provides functionality not yet available in GAP. In many respects,
Carat is complementary to the CrystGap prepackage, and extends its
functionality. If Carat is installed, CrystGap automatically loads
Carat and makes use of it.
The update of CrystGap contains various performance improvements
and a much improved implementation of the normalizer routine for
affine crystallographic groups. The previous version failed in
certain situations and could even produce wrong results.
Updating is therefore highly recommended. Many thanks are due
to Max Neunhoeffer for his extensive testing, which uncovered
these bugs and which also led to many performance improvements.
With kind regards,