GAP 4 Package Wedderga

Central Idempotents and Simple Components of Group Algebras


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 of finite groups over abelian number fields and over finite fields. It also contains functions that compute the primitive central idempotents of the same kind of group algebras, and 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.

The Wedderga package was submitted for consideration to the GAP Council on September 25, 2006. The package became accepted since the version 4.3.3 released on May 29, 2008.

  • Ángel del Río, e-mail: adelrio <at> um <dot> es,
  • Osnel Broche Cristo, e-mail: osnel <at> ufla <dot> br
  • Alexander Konovalov, e-mail: konovalov <at> member <dot> ams <dot> org,
  • Aurora Olivieri, e-mail: olivieri <at> usb <dot> ve
  • Gabriela Olteanu, e-mail: golteanu <at> um <dot> es
If you use Wedderga, we would be grateful for a short notification sent to one of the authors.

(C) 2006 by Ángel del Río, Osnel Broche Cristo, Alexander Konovalov, Aurora Olivieri and Gabriela Olteanu.

For use and distribution of this software, we adopt the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. For details, see the text of the license at FSF's own site

Wedderga documentation is a part of its distribution (see next section). To preview the documentation, select one of the following formats: The file PackageInfo.g with Wedderga package meta-information used by GAP 4.4 package loading mechanism is located here.

Wedderga is designed for GAP4.4 and no compatibility with previous releases of GAP4 is guaranteed. It does not use external binaries and, therefore, works without restriction on type of the opearting system.

To use the Wedderga  online help  it is necessary  to install the GAP4 package GAPDoc by  Frank Luebeck  and  Max Neunhoeffer,  which  is available from the GAP homepage or from

To download Wedderga distribution, select one of the following files:
Further instructions on Wedderga installation can be found in the file README.wedderga here.

Wedderga Bibliography
We maintain a list of references to the Wedderga package. It contains works where the Wedderga package was cited. We will appreciate your additions or corrections to this list sent to one of the Wedderga authors.

If you publish a result that was partially obtained with the help of Wedderga, please cite it in the following form:
O. Broche Cristo, A. Konovalov, A. Olivieri, G. Olteanu and Á. del Río. Wedderga --- Wedderburn Decomposition of Group Algebras, Version 4.3.3; 2009 (

On various stages the development of the Wedderga package was supported by the following institutions:
  • University of Murcia
  • Francqui Stichting grant ADSI107
  • M.E.C. of Romania (CEEX-ET 47/2006)
  • D.G.I. of Spain
  • Fundación Séneca of Murcia
  • CAPES and FAPESP of Brazil
We acknowledge with gratitude this support.

Last updated: 29 May, 2009