diff --git a/doc/ref/groups.xml b/doc/ref/groups.xml index 8ac9bf39c6..3c2809ea91 100644 --- a/doc/ref/groups.xml +++ b/doc/ref/groups.xml @@ -457,6 +457,7 @@ the series without destroying the properties of the series. <#Include Label="NormalSubgroups"> <#Include Label="MaximalNormalSubgroups"> <#Include Label="MinimalNormalSubgroups"> +<#Include Label="CharacteristicSubgroups"> diff --git a/lib/grp.gd b/lib/grp.gd index 1e49bd944b..63d3487d4e 100644 --- a/lib/grp.gd +++ b/lib/grp.gd @@ -1817,7 +1817,7 @@ DeclareAttribute( "NilpotencyClassOfGroup", IsGroup ); ## abelian or solvable, then these should be computed before computing the ## maximal normal subgroups. ## MaximalNormalSubgroups( g ); +## gap> g:=SymmetricGroup(4);; MaximalNormalSubgroups( g ); ## [ Group([ (1,2,3), (2,3,4) ]) ] ## gap> f := FreeGroup("x", "y");; x := f.1;; y := f.2;; ## gap> List(MaximalNormalSubgroups(f/[x^2, y^2]), GeneratorsOfGroup); @@ -1856,7 +1856,7 @@ DeclareAttribute( "NormalMaximalSubgroups", IsGroup ); ## is a list containing those nontrivial normal subgroups of the group G ## that are minimal among the nontrivial normal subgroups. ## MinimalNormalSubgroups( g ); +## gap> g:=SymmetricGroup(4);; MinimalNormalSubgroups( g ); ## [ Group([ (1,4)(2,3), (1,3)(2,4) ]) ] ## ]]> ## @@ -1877,9 +1877,12 @@ DeclareAttribute( "MinimalNormalSubgroups", IsGroup ); ## ## returns a list of all normal subgroups of G. ## g:=SymmetricGroup(4);;NormalSubgroups(g); +## gap> g:=SymmetricGroup(4);; NormalSubgroups(g); ## [ Sym( [ 1 .. 4 ] ), Alt( [ 1 .. 4 ] ), ## Group([ (1,4)(2,3), (1,3)(2,4) ]), Group(()) ] +## gap> g:=AbelianGroup([2,2]);; NormalSubgroups(g); +## [ , Group([ f2 ]), +## Group([ f1*f2 ]), Group([ f1 ]), Group([ ]) ] ## ]]> ##

## The algorithm for the computation of normal subgroups is described in @@ -1902,9 +1905,11 @@ DeclareAttribute( "NormalSubgroups", IsGroup ); ## returns a list of all characteristic subgroups of G, that is ## subgroups that are invariant under all automorphisms. ## g:=SymmetricGroup(4);;NormalSubgroups(g); +## gap> g:=SymmetricGroup(4);; CharacteristicSubgroups(g); ## [ Sym( [ 1 .. 4 ] ), Group([ (2,4,3), (1,4)(2,3), (1,3)(2,4) ]), ## Group([ (1,4)(2,3), (1,3)(2,4) ]), Group(()) ] +## gap> g:=AbelianGroup([2,2]);; CharacteristicSubgroups(g); +## [ , Group([ ]) ] ## ]]> ##

##