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This file describes changes in the GAP package TwistedConjugacy.

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