The Wedderga Package
Osnel Broche Cristo, Allen Herman, Alexander Konovalov, Aurora Olivieri,
Gabriela Olteanu, Ángel del Río and Inneke Van Gelder.
The title "Wedderga" stands for "Wedderburn decomposition of group algebras".
This is a GAP package to compute the simple components of the Wedderburn
decomposition of semisimple group algebras. So the main functions of the
package returns a list of simple algebras whose direct sum is isomorphic to
the group algebra given as input.
The methods implemented by the package produces the Wedderburn decomposition
of a group algebra FG provided G is a finite group and F is either a finite
field of characteristic coprime with the order of G, or an abelian number
field (i.e. a subfield of a finite cyclotomic extension of the rationals).
Other functions of Wedderga compute the primitive central idempotents of
semisimple group algebras and a complete set of orthogonal primitive
The package also provides functions to construct crossed products over a
group with coefficients in an associative ring with identity and the
multiplication determined by a given action and twisting.
Furhermore, the package provides functions to create code words from a group
Installation and system requirements:
Wedderga does not use external binaries and, therefore, works without
restrictions on the type of the operating system. It is designed for GAP4.5
and no compatibility with previous releases of GAP4 is guaranteed.
To use the Wedderga online help it is necessary to install the GAP4 package
GAPDoc by Frank Lübeck and Max Neunhöffer, which is available from the GAP
site or from http://www.math.rwth-aachen.de/~Frank.Luebeck/GAPDoc/.
Wedderga is distributed in standard formats (tar.gz, tar.bz2, -win.zip) and
can be obtained from http://www.cs.st-andrews.ac.uk/~alexk/wedderga/ or
http://www.gap-system.org/Packages/wedderga.html at the GAP web site. To
install Wedderga, unpack its archive into the pkg subdirectory of your GAP
Installation *outside the GAP main directory*: when you don't have access to
the directory of your main GAP installation you can also install the package
by unpacking inside a directory "MYGAPDIR/pkg". Then to be able to load
Wedderga you need to call GAP with the '-l ";MYGAPDIR" option.
Installation using other archive formats is performed in a similar way.
Now you can start GAP and load the Wedderga package using the command:
The Wedderga team