Standard Subgroup Constructions

Some functions described in this section may not exist or may have restrictions for some categories of groups. Details can be found in the chapters on the individual categories.

H ^ g: GrpFin, GrpFinElt -> GrpFin
Conjugate(H, g): GrpFin, GrpFinElt -> GrpFin: Construct the conjugate \(g^{-1}Hg\) of the group \(H\) by the element \(g\). The group \(H\) and the element \(g\) must belong to the same generic group.

H meet K: GrpFin, GrpFin -> GrpFin: Given groups \(H\) and \(K\) which belong to the same symmetric group, construct the intersection of \(H\) and \(K\).

CommutatorSubgroup(G, H, K): GrpFin, GrpFin, GrpFin -> GrpFin
CommutatorSubgroup(H, K): GrpFin, GrpFin -> GrpFin: Given groups \(H\) and \(K\), both subgroups of the group \(G\), construct the commutator subgroup of \(H\) and \(K\) in the group \(G\). If \(K\) is a subgroup of \(H\), then the group \(G\) may be omitted.

Centralizer(G, g): GrpFin, GrpFinElt -> GrpFin
Centraliser(G, g): GrpFin, GrpFinElt -> GrpFin: Construct the centralizer of the element \(g\) in the group \(G\).

Centralizer(G, H): GrpFin, GrpFin -> GrpFin
Centraliser(G, H): GrpFin, GrpFin -> GrpFin: Construct the centralizer of the group \(H\) in the group \(G\).

Core(G, H): GrpFin, GrpFin -> GrpFin: Given a subgroup \(H\) of the group \(G\), construct the maximal normal subgroup of \(G\) that is contained in the subgroup \(H\).

H ^ G: GrpFin, GrpFin -> GrpFin
NormalClosure(G, H): GrpFin, GrpFin -> GrpFin: Given a subgroup \(H\) of the group \(G\), construct the normal closure of \(H\) in \(G\).

Normalizer(G, H): GrpFin, GrpFin -> GrpFin
Normaliser(G, H): GrpFin, GrpFin -> GrpFin: Given a subgroup \(H\) of the group \(G\), construct the normalizer of \(H\) in \(G\).

pCore(G, p): GrpFin, RngIntElt -> GrpFin: Given a group \(G\) and a prime \(p\) dividing the order of \(G\), construct the maximal normal \(p\)-subgroup of \(G\).

SylowSubgroup(G, p): GrpFin, RngIntElt -> GrpFin
Sylow(G, p): GrpFin, RngIntElt -> GrpFin: Given a group \(G\) and a prime \(p\), construct a Sylow \(p\)-subgroup of \(G\).

Abstract Group Predicates

Some functions described in this section may not exist or may have restrictions for some categories of groups. Details can be found in the chapters on the individual categories.

IsAbelian(G): GrpFin -> BoolElt: Returns true if the group \(G\) is abelian, false otherwise.

IsCyclic(G): GrpFin -> BoolElt: Returns true if the group \(G\) is cyclic, false otherwise.

IsElementaryAbelian(G): GrpFin -> BoolElt: Returns true if the group \(G\) is elementary abelian, false otherwise.

IsCentral(G, H): GrpFin, GrpFin -> BoolElt: Return true if the subgroup \(H\) of the group \(G\) lies in the centre of \(G\), false otherwise.

IsConjugate(G, g, h): GrpFin, GrpFinElt, GrpFinElt -> BoolElt, GrpFinElt: Given a group \(G\) and elements \(g\) and \(h\) belonging to \(G\), return the value true if \(g\) and \(h\) are conjugate in \(G\). The function returns a second value if the elements are conjugate: an element \(k\) which conjugates \(g\) into \(h\). For permutation groups it is sufficient that \(G\), \(g\), and \(h\) have a common covering group.

IsConjugate(G, H, K): GrpFin, GrpFin, GrpFin -> BoolElt, GrpFinElt: Given a group \(G\) and subgroups \(H\) and \(K\) belonging to \(G\), return the value true if \(H\) and \(K\) are conjugate in \(G\). The function returns a second value if the subgroups are conjugate: an element \(z\) which conjugates \(H\) into \(K\). For permutation groups it is sufficient that \(G\), \(H\), and \(K\) have a common covering group.

IsExtraSpecial(G): GrpFin -> BoolElt: Given a group \(G\) is a \(p\)-group \(G\), return true if \(G\) is extra-special, false otherwise.

IsHyperelementary(G): Grp -> BoolElt, Grp, Grp

p: RngIntElt                    Default: 0

Test if \(G\) is a finite hyperelementary (=quasi-elementary) group, that is a semi-direct product \(G=C:P\) with \(C\) cyclic and \(P\) a \(p\)-group of order coprime to \(C\). If yes, returns true, \(C\), \(P\). Otherwise returns false. The prime number \(p\) can be forced with an optional parameter \(p\) (\(0\) by default).

Example: Hyperelementary Groups (ex-d7354f)

> ok,C,P:=IsHyperelementary(Sym(3));   // S3=C3:C2 is hyperelementary
> ok,GroupName(C),GroupName(P);
true C3 C2
> ok,C,P:=IsHyperelementary(Sylow(Sym(6),2));    // So is any p-group
> ok,GroupName(C),GroupName(P);
true C1 C2*D4
> IsHyperelementary(Sym(4));             // S4 is not hyperelementary
false

Run in calculator (opens in a new tab)

IsMaximal(G, H): GrpFin, GrpFin -> BoolElt: Returns true if the subgroup \(H\) of the group \(G\) is a maximal subgroup of \(G\). This function is evaluated by constructing the permutation representation of \(G\) on the cosets of \(H\) and testing this representation for primitivity. For this reason, the use of IsMaximal should be avoided if the index of \(H\) in \(G\) exceeds a one hundred thousand.

IsNilpotent(G): GrpFin -> BoolElt: Return true if the group \(G\) is nilpotent, false otherwise.

IsNormal(G, H): GrpFin, GrpFin -> BoolElt: Return true if the subgroup \(H\) of the group \(G\) is a normal subgroup of \(G\), false otherwise.

IsPerfect(G): GrpFin -> BoolElt: Return true if the group \(G\) is perfect, false otherwise.

IsQGroup(G): Grp -> BoolElt: Returns true if the group \(G\) is a \({\mathbb{Q}}\)-group (all characters are rational-valued).

Example: Testing for Q-Groups (ex-694ffe)

> IsQGroup(Sym(4));         // Symmetric groups S_n are Q-groups
true
> IsQGroup(Alt(4));         // and alternating groups A_n are not (for n>2)
false

Run in calculator (opens in a new tab)

IsSelfNormalizing(G, H): GrpFin, GrpFin -> BoolElt
IsSelfNormalising(G, H): GrpFin, GrpFin -> BoolElt: Return true if the subgroup \(H\) of the group \(G\) is self-normalizing in \(G\), false otherwise.

IsSimple(G): GrpFin -> BoolElt: Return true if the group \(G\) is simple, false otherwise.

IsSoluble(G): GrpFin -> BoolElt
IsSolvable(G): GrpFin -> BoolElt: Return true if the group \(G\) is soluble, false otherwise.

IsSpecial(G): GrpFin -> BoolElt: Given a \(p\)-group \(G\), return true if \(G\) is special, false otherwise.

IsAbstractFrobeniusGroup(G): GrpFin -> BoolElt, Grp, Grp: Is the finite group \(G\) a Frobenius group as an abstract group? Equivalently, does there exist a faithful permutation representation of \(G\) for which the image is a Frobenius group as a permutation group? If so, then return true, a Frobenius kernel, and a corresponding Frobenius complement; otherwise return false.

IsSubnormal(G, H): GrpFin, GrpFin -> BoolElt: Return true if the subgroup \(H\) of the group \(G\) is subnormal in \(G\), false otherwise.

IsTrivial(G): Grp -> BoolElt: Return true if \(G\) is trivial, false otherwise.

Standard Subgroup Constructions#

Abstract Group Predicates#

Standard Subgroup Constructions

Abstract Group Predicates