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1 The TwistedConjugacy package

This is the manual for the GAP 4 package TwistedConjugacy version 3.4.1, developed by Sam Tertooy.

1.1 Installation

If you are using GAP version 4.15.0 or newer, then TwistedConjugacy should be installed by default.

If this is not the case, but the PackageManager package is installed and loaded, you can install TwistedConjugacy from within a GAP session using InstallPackage (PackageManager 2.1-1).

gap> InstallPackage( "TwistedConjugacy" );
...
true

Alternatively, you can download TwistedConjugacy as a .tar.gz archive here. After extracting, you should place it in a suitable pkg folder. To install it for just yourself, you can place it in $HOME/.gap/pkg (on many Linux distros) or %USERPROFILE%/_gap/pkg (on Windows). To install it for all users, it must be placed in the GAP installation directory (gap-X.Y.Z/pkg).

1.2 Loading

Once installed, loading TwistedConjugacy can be done by using LoadPackage (ref 76.2-1).

gap> LoadPackage( "TwistedConjugacy" );
...
true

1.3 Citing

If you use the TwistedConjugacy package in your research, we would love to hear about your work via an email to the address sam.tertooy@kuleuven.be. If you have used the TwistedConjugacy package in the preparation of a paper and wish to refer to it, please cite it as described below.

In BibTeX:

@misc{TC3.4.1,
   author       = {Tertooy, Sam},
   title        = {{TwistedConjugacy,
                    Computation with twisted conjugacy classes,
                    Version 3.4.1}},
   note         = {GAP package},
   year         = {2026},
   howpublished = {\url{https://stertooy.github.io/TwistedConjugacy}}
}

In BibLaTeX:

@software{TC3.4.1,
   author   = {Tertooy, Sam},
   title    = {TwistedConjugacy},
   subtitle = {Computation with twisted conjugacy classes},
   version  = {3.4.1},
   note     = {GAP package},
   year     = {2026},
   url      = {https://stertooy.github.io/TwistedConjugacy}
}

1.4 Support

If you encounter any problems, please submit them to the issue tracker. If you have any questions on the usage or functionality of TwistedConjugacy, you may contact me via email at sam.tertooy@kuleuven.be.

Bugs in GAP, in this package, or in any other package used directly or indirectly, may cause functions provided by TwistedConjugacy to produce errors or incorrect results. To help detect such issues, you can enable internal checks by setting the variable TWC.ASSERT to true. Note that this will come at the cost of reduced performance.

For additional safety, you can enable GAP's built-in assertion features by calling SetAssertionLevel( lev ) (we recommend setting lev to 2) and, when working with PcpGroups, setting the variables CHECK_CENT@Polycyclic, CHECK_IGS@Polycyclic and CHECK_INTSTAB@Polycyclic to true.

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