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MODULES OVER A MATRIX ALGEBRA

 
Acknowledgements
 
Introduction
 
Construction of an A-Module
      General Constructions
      Constructions for K[G]-Modules
 
Accessing Module Information
      The Underlying Vector Space
      The Algebra
 
Standard Constructions
      Changing the Coefficient Ring
      Direct Sum
      Changing Basis
 
Element Construction and Operations
      Construction of Module Elements
      Deconstruction of Module Elements
      Action of the Algebra on the Module
      Arithmetic with Module Elements
      Indexing
      Properties of Module Elements
 
Submodules
      Construction
      Membership and Equality
      Operations on Submodules
 
Quotient Modules
 
Structure of a Module
      Reducibility
      Composition Series
      Socle Series
 
Decomposabilty and Complements
 
Lattice of Submodules
      Creating Lattices
      Operations on Lattices
      Operations on Lattice Elements
      Properties of Lattice Elements
 
Homomorphisms
      Creating Homomorphisms
      Hom(M, N)
      Endo-- and Automorphisms







DETAILS

 
Introduction

 
Construction of an A-Module

      General Constructions
            RModule(A) : AlgMat -> ModTupRng
            RModule(Q) : [ AlgMatElt ] -> ModTupRng
            Example ModAlg_CreateK6 (H71E1)

      Constructions for K[G]-Modules
            GModule(G, Q) : Grp, [ GrpMatElt ] -> ModGrp
            PermutationModule(G, K) : Grp, Fld -> ModGrp

 
Accessing Module Information

      The Underlying Vector Space
            VectorSpace(M) : ModTupRng -> ModTupRng
            M . i : ModTupRng, RngIntElt -> ModElt
            CoefficientRing(M) : ModTupRng -> Rng
            Generators(M) : ModTupRng -> { ModTupElt }
            Parent(u) : ModTupElt -> ModRng

      The Algebra
            Algebra(M) : ModTupRng -> Rng
            Action(M) : ModTupRng -> AlgMat
            MatrixGroup(M) : ModGrp -> GrpMat
            ActionGenerator(M, i) : ModTupRng, RngIntElt -> AlgMatElt
            NumberOfActionGenerators(M) : ModTupRng -> RngIntElt
            Group(M) : ModGrp -> Grp
            Example ModAlg_Access (H71E2)

 
Standard Constructions

      Changing the Coefficient Ring
            ChangeRing(M, S) : ModRng, Rng -> ModRng, Map
            ChangeRing(M, S, f) : ModRng, Rng, Map -> ModRng, Map

      Direct Sum
            DirectSum(M, N) : ModRng, ModRng -> ModRng, Map, Map, Map, Map
            DirectSum(Q) : [ ModRng ] -> [ ModRng ], [ Map ], [ Map ]

      Changing Basis
            M ^ T : ModGrp, AlgMatElt -> ModGrp

 
Element Construction and Operations

      Construction of Module Elements
            elt< M | a_1, ..., a_n > : ModTupRng, List -> ModTupRngElt
            M ! Q : ModTupRng, [RngElt] -> ModTupRngElt
            Zero(M) : ModRng, RngIntElt -> ModRngElt
            Random(M) : ModRng -> ModRngElt

      Deconstruction of Module Elements
            ElementToSequence(u) : ModTupRngElt -> [RngElt]

      Action of the Algebra on the Module
            u * a : ModTupElt, AlgElt -> ModTupElt
            u * g : ModGrpElt, GrpElt -> ModGrpElt

      Arithmetic with Module Elements
            u + v : ModTupElt, ModTupElt -> ModTupElt
            - u : ModTupElt -> ModTupElt
            u - v : ModTupElt, ModTupElt -> ModTupElt
            k * u : RngElt, ModTupElt -> ModTupElt
            u * k : ModTupElt, RngElt -> ModTupElt
            u / k : ModTupElt, RngElt -> ModTupElt

      Indexing
            u[i] : ModTupRngElt, RngIntElt -> RngElt
            u[i] := x : ModTupRngElt, RngIntElt, RngElt -> ModTupRngElt

      Properties of Module Elements
            IsZero(u) : ModTupElt -> BoolElt
            Support(u) : ModTupRngElt -> { RngElt }

 
Submodules

      Construction
            sub<M | L> : ModTupRng, List -> ModTupRng
            ImageWithBasis(X, M) : ModMatRngElt, ModRng -> ModRng
            Morphism(M, N) : ModRng, ModRng -> ModMatRngElt
            Example ModAlg_Submodule (H71E3)

      Membership and Equality
            u in M : ModTupRngElt, ModTupRng -> BoolElt
            N subset M : ModTupRng, ModTupRng -> BoolElt
            N eq M : ModTupRng, ModTupRng -> BoolElt

      Operations on Submodules
            M + N : ModTupRng, ModTupRng -> ModTupRng
            M meet N : ModTupRng, ModTupRng -> ModTupRng

 
Quotient Modules
      quo<M | L> : ModTupRng, List -> ModTupRng
      Morphism(M, N) : ModRng, ModRng -> ModMatRngElt
      Example ModAlg_QuotientModule (H71E4)

 
Structure of a Module

      Reducibility
            Meataxe(M) : ModRng -> ModRng, ModRng, AlgMatElt
            IsIrreducible(M) : ModRng -> BoolElt, ModRng, ModRng
            IsAbsolutelyIrreducible(M) : ModRng -> BoolElt, AlgMatElt, RngIntElt
            AbsolutelyIrreducibleModule(M) : ModRng -> ModRng
            Example ModAlg_Meataxe (H71E5)
            MinimalField(M) : ModRng -> FldFin

      Composition Series
            CompositionSeries(M) : ModRng, ModRng -> [ ModRng ], [ ModRng ], AlgMatElt
            CompositionFactors(M) : ModRng -> [ ModRng ]
            Constituents(M) : ModRng -> [ ModRng ]
            ConstituentsWithMultiplicities(M) : ModRng -> [ <ModRng, RngIntElt> ]
            Example ModAlg_CompSeries (H71E6)

      Socle Series
            IsSemisimple(M) : ModGrp -> BoolElt
            MaximalSubmodules(M) : ModRng -> [ ModRng ], BoolElt
            JacobsonRadical(M) : ModRng -> ModRng
            MinimalSubmodules(M) : ModRng -> [ ModRng ], BoolElt
            MinimalSubmodules(M, F) : ModRng, ModRng -> [ ModRng ], BoolElt
            MinimalSubmodule(M) : ModRng -> ModRng
            Socle(M) : ModRng -> ModRng
            SocleSeries(M) : ModRng -> [ ModRng ], [ ModRng ], AlgMatElt
            SocleFactors(M) : ModRng -> [ ModRng ]
            Example ModAlg_Minimals (H71E7)

 
Decomposabilty and Complements
      IsDecomposable(M) : ModRng -> BoolElt, ModRng, ModRng
      IndecomposableSummands(M) : ModGrp -> [ ModGrp ]
      HasComplement(M, S) : ModGrp, ModGrp -> BoolElt, ModGrp
      Complements(M, S) : ModGrp, ModGrp -> [ ModGrp ]
      Example ModAlg_Decomposable (H71E8)

 
Lattice of Submodules

      Creating Lattices
            SubmoduleLattice(M) : ModRng -> SubModLat, BoolElt
            SubmoduleLatticeAbort(M, n) : ModRng, RngIntElt -> BoolElt, SubModLat
            SetVerbose("SubmoduleLattice", i) : MonStgElt, RngIntElt ->
            Submodules(M) : ModRng -> [ModRng]
            Example ModAlg_CreateLattice (H71E9)

      Operations on Lattices
            # L : SubModLat -> RngIntElt
            L ! i: SubModLat, RngIntElt -> SubModLatElt
            L ! S: SubModLat, ModRng -> SubModLatElt
            Bottom(L): SubModLat -> SubModLatElt
            Random(L): SubModLat -> SubModLatElt
            Top(L): SubModLat -> SubModLatElt

      Operations on Lattice Elements
            IntegerRing() ! e : SubModLatElt -> RngIntElt
            e + f : SubModLatElt, SubModLatElt -> SubModLatElt
            e meet f : SubModLatElt, SubModLatElt -> SubModLatElt
            e eq f : SubModLatElt, SubModLatElt -> SubModLatElt
            e subset f : SubModLatElt, SubModLatElt -> SubModLatElt
            MaximalSubmodules(e) : SubModLatElt -> { SubModLatElt }
            MinimalSupermodules(e) : SubModLatElt -> { SubModLatElt }
            Module(e) : SubModLatElt -> ModRng

      Properties of Lattice Elements
            Dimension(e) : SubModLatElt -> RngIntElt
            JacobsonRadical(e) : SubModLatElt -> SubModLatElt
            Morphism(e) : SubModLatElt -> ModMatRngElt
            Example ModAlg_LatticeOps (H71E10)

 
Homomorphisms

      Creating Homomorphisms
            hom< M -> N | X > : ModRng, ModRng, ModMatElt -> ModMatRng
            H ! f : ModMatRng, Map -> ModMatRngElt
            IsModuleHomomorphism(X) : ModMatElt -> BoolElt

      Hom(M, N)
            Hom(M, N) : ModRng, ModRng -> ModMatRng
            AHom(M, N) : ModGrp, ModGrp -> ModMatGrp
            GHomOverCentralizingField(M, N) : ModGrp, ModGrp -> ModMatGrp
            Example ModAlg_EndoRing (H71E11)
            Example ModAlg_CreateHomGHom (H71E12)

      Endo-- and Automorphisms
            EndomorphismAlgebra(M) : ModRng -> AlgMat
            AutomorphismGroup(M) : ModRng -> AlgMat
            IsIsomorphic(M, N) : ModRng, ModRng -> BoolElt, AlgMatElt
            Example ModAlg_EndoRing (H71E13)