RCWA -- [R]esidue-[C]lass-[W]ise [A]ffine groups
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                           -- A GAP 4 Package --

                               Version 3.1.1

        Author and Maintainer:  Stefan Kohl, stefan@mcs.st-and.ac.uk


                                  Abstract

This package for GAP 4 provides implementations of algorithms and methods for
computing in certain  infinite permutation groups  acting on the set of inte-
gers.  In principle it can deal with at least the following  types of groups:

 - Finite groups.
 - Free groups of finite rank.
 - Free products of finitely many finite groups, thus in particular
   the modular group PSL(2,Z).
 - Direct products of such groups.
 - Wreath products of such groups with finite groups and with (Z,+).

Among these groups there are finitely generated groups which are not finitely
presented, and such with  unsolvable membership problem.  Further, any finite
group embeds into some divisible torsion group which RCWA can deal with.
    With the help of  this package,  the author has found  a countable simple
group which is generated by involutions interchanging disjoint  residue clas-
ses of the integers and which all the above groups embed into.
    For details on how to use the RCWA package, see the package documentation
in the `doc' subdirectory --  either view its  HTML version (chap0.html) with
a browser, or its PDF version (manual.pdf) with a PDF viewer.


                                Requirements

This version of RCWA needs at least GAP 4.5.2,  ResClasses 3.0.2,  GRAPE 4.3,
Polycyclic 2.6  and GAPDoc 1.4.  All required packages are already present in
a standard GAP installation. RCWA can be used  under UNIX,  under Windows and
on  the MacIntosh.  It is completely  written  in the  GAP language  and does
neither contain nor require  external binaries.  Warnings concerning  missing
binaries issued by GRAPE or other packages can savely be ignored.


                                Installation

Like any other GAP package,  RCWA must be installed in the pkg/  subdirectory
of the GAP distribution.  This is accomplished by extracting the  package ar-
chive file in this directory.  After this  you can load  the package as usual
via LoadPackage( "rcwa" );.
    For further advice  on questions of technical nature please see the chap-
ter `Installation and Auxiliary Functions' in the manual.


                          Distribution and Updates

New releases of this package are put online on the package web page

       http://www.gap-system.org/DevelopersPages/StefanKohl/rcwa.html

                                     ---

If you install RCWA or if you use it in some of your work, then please let me
know. -- I am interested very much in any applications of this package.  Also
please let me know  if you have problems with this package,  or if you find a
bug.

Stefan Kohl,  October 2011