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This file describes changes in the GAP package TwistedConjugacy.
3.1.1 (2025-10-12)
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- Assertion variable renamed (again) to `TWC.ASSERT`
- Affine actions can now be compared using the equality (`=`)
operator
- Update license text to latest version
- Update installation instructions in manual
- More changes to file structure
- Small improvements to the documentation of derivations and affine
actions
- Janitorial changes
3.1.0 (2025-09-14)
------------------
- Now requires Polycyclic version >= 2.17
- Functionality for affine actions added
- Assertion variable renamed to `TWC_ASSERT`
- Ensured that this package does not break the Polycyclic test suite
- Package tests no longer require the SmallGrp and TransGrp packages
- Large changes to file structure
3.0.0 (2025-07-21)
------------------
- Now requires GAP version >= 4.14
- Switched the order of the homomorphisms in the definition of the twisted
conjugation action, which is very likely to break scripts relying on older
versions of this package
- Added method for (Representatives)ReidemeisterClasses and ReidemeisterNumber
with no restrictions on the homomorphisms or the source and target groups
- (Representatives)ReidemeisterClasses now accepts a normal subgroup as
optional input, and will then only return the (representatives of the)
Reidemeister classes that intersect this normal subgroup
- RepresentativeTwistedConjugation and IsTwistedConjugate again accept lists as
input, replacing the need for the separate functions
RepresentativeTwistedConjugationMultiple and IsTwistedConjugateMultiple
- Added more methods related to double cosets (of PcpGroups)
- Added methods related to group derivations between finite groups and between
PcpGroups
- Improved the efficiency of CoincidenceGroup in certain cases
- Improved the efficiency of CoincidenceReidemeisterSpectrum for non-abelian
groups
- Overhauled the documentation
- Many smaller changes
2.4.0 (2024-12-05)
------------------
- Added methods for intersections of arbitrary subgroups and cosets in
PcpGroups
- Added method to test membership in a double coset of a PcpGroup
- Algorithms for infinite polycyclic groups again require the Polycyclic
package, since many methods would otherwise run forever due to the lack of
finiteness checks in existing methods
- Renamed FullReidemeisterSpectrum to TotalReidemeisterSpectrum, to avoid
confusion with a spectrum being 'full'
- Replaced ToggleSafeMode@TwistedConjugacy by variable ASSERT@TwistedConjugacy
2.3.0 (2024-09-17)
------------------
- Now requires GAP version >= 4.13
- Polycyclic version >= 2.16 is now an extension instead of a suggested package
- Added FullReidemeisterSpectrum
- Documented RepresentativesReidemeisterClasses
- Added ToggleSafeMode@TwistedConjugacy, to use built-in assertions (including
those in Polycyclic) to check for any errors.
2.2.0 (2024-02-13)
------------------
- Now requires GAP version >= 4.12 and optionally Polycyclic version >= 2.16
- ReidemeisterSpectrum is now much more efficient for (large) non-abelian
groups
- RepresentativeTwistedConjugation and IsTwistedConjugate no longer take lists
as input, this functionality has been moved to new functions called
RepresentativeTwistedConjugationMultiple and IsTwistedConjugateMultiple
- Added IsNilpotentByFinite and IsPolycyclicByFinite properties
- Code for infinite groups is now less dependent on the Polycyclic package
being loaded
2.1.0 (2023-03-16)
------------------
- Now requires GAP version >= 4.11 and optionally polycyclic version >= 2.15.1
- Many efficiency improvements, both speed- and memory-related. In particular
calculating Reidemeister spectra of finite groups should be much faster
- Added RepresentativeAutomorphismClasses, RepresentativesEndomorphismClasses
and RepresentativesHomomorphismClasses, which can be applied to finite
groups. They give output similar to GAP's built-in AllHomomorphismClasses
function, but should be faster for abelian and non-2-generated groups
- Fixed a bug that made ReidemeisterSpectrum not work for the trivial group
- CoincidenceGroup, RepresentativeTwistedConjugation and IsTwistedConjugate
now work for any pair of endomorphisms between any two polycyclic groups
- FixedPointGroup now works for any endomorphism of any polycyclic group
- CoincidenceGroup can now take 3 or more endomorphisms as argument
- RepresentativeTwistedConjugation and IsTwistedConjugate can now take lists
as input, and will try to solve the multiple twisted conjugacy problem
2.0.0 (2021-05-01)
------------------
- Lowered requirements to GAP version >= 4.9 and GAPDoc version >= 1.6.1
- Polycyclic is now a suggested package instead of required. Version >= 2.13.1
is required, although version >= 2.16 is recommended
- AutoDoc is now a suggested package, version >= 2018.02.14 is required
- The documentation has been largely rewritten.
- Changed how the manual is generated. The manual can be recreated using
AutoDoc by running the "makedoc.g" script in the main package directory
- Renamed "gap" subfolder to "lib"
- Improved available tests
- IsTwistedConjugate can now always be applied to homomorphisms between
distinct groups. A result is only guaranteed, however, if the range is
nilpotent-by-finite or if the homomorphisms are endomorphisms with finite
Reidemeister number
- ReidemeisterClasses can now always be applied to homomorphisms between
distinct groups. A result is only guaranteed, however, if the range is
nilpotent-by-finite or if the homomorphisms are endomorphisms
- Applying "Size" to an infinite Reidemeister class will now return "infinity"
instead of running indefinitely, if the range is nilpotent-by-finite
- Implemented "StabiliserOfExternalSet" for Reidemeister classes
- Improved calculation of Reidemeister numbers for (finite) abelian groups
- Improved calculation of Reidemeister spectra for finite abelian groups
- Added CoincidenceReidemeisterSpectrum
- Significant improvements in calculation time for
ExtendedReidemeisterSpectrum
- Reidemeister Zeta functions expanded to pairs of endomorphisms of finite
groups, instead of a single endomorphism
- Changed the output of ReidemeisterZetaCoefficients to accommodate for the
above change
- Added IsRationalReidemeisterZeta
- ReidemeisterZeta now returns either a rational function or "fail"
- CoincidenceGroup is much more efficient for homomorphisms between finite
groups
- CoincidenceGroup can now always be applied to homomorphisms between
distinct groups. A result is only guaranteed, however, if the range is
nilpotent-by-finite or if the homomorphisms are endomorphisms with finite
Reidemeister number
- InducedEndomorphism and RestrictedEndomorphism replaced by the more general
InducedHomomorphism and RestrictedHomomorphism respectively
- Finite PcpGroups will now automatically be converted to PcGroups
1.0.1 (2020-06-07)
------------------
- Improvements to PrintObj for ReidemeisterClasses
- Test Suite now has full coverage
- Some functions in HelpFunctions.gi now have local scope
- Updated documentation to include examples
1.0.0 (2020-02-19)
------------------
- Initial release
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