Goto Chapter: Top 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 Ind
 [Top of Book]  [Contents]   [Previous Chapter]   [Next Chapter] 

8 Functors

8 Functors

ExtendScalars(R,G,EltsG)

Inputs a ZH-resolution R, a group G containing H as a subgroup, and a list EltsG of elements of G. It returns the free ZG-resolution (R ⊗_ZH ZG). The returned resolution S has S!.elts:=EltsG. This is a resolution of the ZG-module (Z ⊗_ZH ZG). (Here ⊗_ZH means tensor over ZH.)

HomToIntegers(X)

Inputs either a ZG-resolution X=R, or an equivariant chain map X = (F:R ⟶ S). It returns the cochain complex or cochain map obtained by applying HomZG( _ , Z) where Z is the trivial module of integers (characteristic 0).

HomToIntegersModP(R)

Inputs a ZG-resolution R and returns the cochain complex obtained by applying HomZG( _ , Z_p) where Z_p is the trivial module of integers mod p. (At present this functor does not handle equivariant chain maps.)

HomToIntegralModule(R,f)

Inputs a ZG-resolution R and a group homomorphism f:G ⟶ GL_n(Z) to the group of n×n invertible integer matrices. Here Z must have characteristic 0. It returns the cochain complex obtained by applying HomZG( _ , A) where A is the ZG-module Z^n with G action via f. (At present this function does not handle equivariant chain maps.)

TensorWithIntegralModule(R,f)

Inputs a ZG-resolution R and a group homomorphism f:G ⟶ GL_n(Z) to the group of n×n invertible integer matrices. Here Z must have characteristic 0. It returns the chain complex obtained by tensoring over ZG with the ZG-module A=Z^n with G action via f. (At present this function does not handle equivariant chain maps.)

HomToGModule(R,A)

Inputs a ZG-resolution R and an abelian G-outer group A. It returns the G-cocomplex obtained by applying HomZG( _ , A). (At present this function does not handle equivariant chain maps.)

InduceScalars(R,hom)

Inputs a ZQ-resolution R and a surjective group homomorphism hom:G→ Q. It returns the unduced non-free ZG-resolution.

LowerCentralSeriesLieAlgebra(G) LowerCentralSeriesLieAlgebra(f)

Inputs a pcp group G. If each quotient G_c/G_c+1 of the lower central series is free abelian or p-elementary abelian (for fixed prime p) then a Lie algebra L(G) is returned. The abelian group underlying L(G) is the direct sum of the quotients G_c/G_c+1 . The Lie bracket on L(G) is induced by the commutator in G. (Here G_1=G, G_c+1=[G_c,G] .)

The function can also be applied to a group homomorphism f: G ⟶ G' . In this case the induced homomorphism of Lie algebras L(f):L(G) ⟶ L(G') is returned.

If the quotients of the lower central series are not all free or p-elementary abelian then the function returns fail.

This function was written by Pablo Fernandez Ascariz

TensorWithIntegers(X)

Inputs either a ZG-resolution X=R, or an equivariant chain map X = (F:R ⟶ S). It returns the chain complex or chain map obtained by tensoring with the trivial module of integers (characteristic 0).

FilteredTensorWithIntegers(R)

Inputs a ZG-resolution R for which "filteredDimension" lies in NamesOfComponents(R). (Such a resolution can be produced using TwisterTensorProduct(), ResolutionNormalSubgroups() or FreeGResolution().) It returns the filtered chain complex obtained by tensoring with the trivial module of integers (characteristic 0).

TensorWithTwistedIntegers(X,rho)

Inputs either a ZG-resolution X=R, or an equivariant chain map X = (F:R ⟶ S). It also inputs a function rho: G→ Z where the action of g ∈ G on Z is such that g.1 = rho(g). It returns the chain complex or chain map obtained by tensoring with the (twisted) module of integers (characteristic 0).

TensorWithIntegersModP(X,p)

Inputs either a ZG-resolution X=R, or a characteristics 0 chain complex, or an equivariant chain map X = (F:R ⟶ S), or a chain map between characteristic 0 chain complexes, together with a prime p. It returns the chain complex or chain map obtained by tensoring with the trivial module of integers modulo p.

TensorWithTwistedIntegersModP(X,p,rho)

Inputs either a ZG-resolution X=R, or an equivariant chain map X = (F:R ⟶ S), and a prime p. It also inputs a function rho: G→ Z where the action of g ∈ G on Z is such that g.1 = rho(g). It returns the chain complex or chain map obtained by tensoring with the trivial module of integers modulo p.

TensorWithRationals(R)

Inputs a ZG-resolution R and returns the chain complex obtained by tensoring with the trivial module of rational numbers.


 


 [Top of Book]  [Contents]   [Previous Chapter]   [Next Chapter] 
Goto Chapter: Top 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 Ind

generated by GAPDoc2HTML