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# This file belongs to ALCO: Tools for Algebraic Combinatorics.
# Copyright (C) 2024, Benjamin Nasmith # This program is free software: you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation, either version 3 of the License, or # (at your option) any later version. # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # You should have received a copy of the GNU General Public License # along with this program. If not, see <https://www.gnu.org/licenses/>. # Cyclotomic tools BindGlobal( "EisensteinIntegers", Objectify( NewType( CollectionsFamily(CyclotomicsFamily), IsEisensteinIntegers and IsAttributeStoringRep ), rec() ) ); SetLeftActingDomain( EisensteinIntegers, Integers ); SetName( EisensteinIntegers, "EisensteinIntegers" ); SetString( EisensteinIntegers, "EisensteinIntegers" ); SetIsLeftActedOnByDivisionRing( EisensteinIntegers, false ); SetSize( EisensteinIntegers, infinity ); SetGeneratorsOfRing( EisensteinIntegers, [ E(3) ] ); SetGeneratorsOfLeftModule( EisensteinIntegers, [ 1, E(3) ] ); SetIsFinitelyGeneratedMagma( EisensteinIntegers, false ); SetUnits( EisensteinIntegers, Set([ -1, 1, -E(3), E(3), -E(3)^2, E(3)^2 ] )); SetIsWholeFamily( EisensteinIntegers, false ); InstallMethod( \in, "for Eisenstein integers", IsElmsColls, [ IsCyc, IsEisensteinIntegers ], function( cyc, EisensteinIntegers ) return IsCycInt( cyc ) and 3 mod Conductor( cyc ) = 0; end ); InstallMethod( IsEisenInt, "for cyclotomics", [ IsCyc ], function(x) return x in EisensteinIntegers; end); InstallMethod( Basis, "for Eisenstein integers (delegate to `CanonicalBasis')", [ IsEisensteinIntegers ], CANONICAL_BASIS_FLAGS, CanonicalBasis ); InstallMethod( CanonicalBasis, "for Eisenstein integers", [ IsEisensteinIntegers ], function( EisensteinIntegers ) local B; B:= Objectify( NewType( FamilyObj( EisensteinIntegers ), IsFiniteBasisDefault and IsCanonicalBasis and IsCanonicalBasisEisensteinIntegersRep ), rec() ); SetUnderlyingLeftModule( B, EisensteinIntegers ); SetIsIntegralBasis( B, true ); SetBasisVectors( B, Immutable( [ 1, E(3) ] ) ); B!.conductor:= 3; B!.zumbroichbase := [ 0, 1 ]; # Return the basis. return B; end ); InstallMethod( Coefficients, "for the canonical basis of Eisenstein integers", [ IsCanonicalBasisEisensteinIntegersRep, IsCyc ], 0, function( B, v ) return Coefficients(Basis(CF(3), BasisVectors(B)), v); end ); BindGlobal( "KleinianIntegers", Objectify( NewType( CollectionsFamily(CyclotomicsFamily), IsKleinianIntegers and IsAttributeStoringRep ), rec() ) ); SetLeftActingDomain( KleinianIntegers, Integers ); SetName( KleinianIntegers, "KleinianIntegers" ); SetString( KleinianIntegers, "KleinianIntegers" ); SetIsLeftActedOnByDivisionRing( KleinianIntegers, false ); SetSize( KleinianIntegers, infinity ); SetGeneratorsOfRing( KleinianIntegers, [ 1, EB(7) ] ); SetGeneratorsOfLeftModule( KleinianIntegers, [ 1, EB(7) ] ); SetIsFinitelyGeneratedMagma( KleinianIntegers, false ); SetUnits( KleinianIntegers, Set([ -1, 1 ] )); SetIsWholeFamily( KleinianIntegers, false ); InstallMethod( IsKleinInt, "for cyclotomics", [ IsCyc ], function(x) if DegreeOverPrimeField(Field(Union(Basis(KleinianIntegers), [x]))) > 2 then return false; fi; return ForAll(Coefficients(Basis(KleinianIntegers), x), IsInt); end); InstallMethod( \in, "for Kleinian integers", IsElmsColls, [ IsCyc, IsKleinianIntegers ], function( cyc, KleinianIntegers ) return IsKleinInt( cyc ); end ); InstallMethod( Basis, "for Kleinian integers (delegate to `CanonicalBasis')", [ IsKleinianIntegers ], CANONICAL_BASIS_FLAGS, CanonicalBasis ); InstallMethod( CanonicalBasis, "for Kleinian integers", [ IsKleinianIntegers ], function( KleinianIntegers ) local B; B:= Objectify( NewType( FamilyObj( KleinianIntegers ), IsFiniteBasisDefault and IsCanonicalBasis and IsCanonicalBasisKleinianIntegersRep ), rec() ); SetUnderlyingLeftModule( B, KleinianIntegers ); SetIsIntegralBasis( B, true ); SetBasisVectors( B, Immutable( [ 1, EB(7) ] ) ); return B; end ); InstallMethod( Coefficients, "for the canonical basis of IcosianRing", [ IsCanonicalBasisKleinianIntegersRep, IsCyc ], 0, function( B, v ) return Coefficients(Basis(Field(EB(7)), BasisVectors(B)), v); end ); # Quaternion tools InstallMethod( Trace, "for a quaternion", [ IsQuaternion and IsSCAlgebraObj ], quat -> ExtRepOfObj(quat + ComplexConjugate(quat))[1] ); InstallMethod( Norm, "for a quaternion", [ IsQuaternion and IsSCAlgebraObj ], quat -> ExtRepOfObj(quat*ComplexConjugate(quat))[1] ); BindGlobal( "QuaternionD4Basis", Basis(QuaternionAlgebra(Rationals), List([ [ -1/2, -1/2, -1/2, 1/2 ], [ -1/2, -1/2, 1/2, -1/2 ], [ -1/2, 1/2, -1/2, -1/2 ], [ 1, 0, 0, 0 ] ], x -> ObjByExtRep(FamilyObj(One(QuaternionAlgebra(Rationals))),x) )) ); BindGlobal( "HurwitzIntegers", Objectify( NewType( CollectionsFamily(FamilyObj(QuaternionAlgebra(Rationals))), IsHurwitzIntegers and IsRingWithOne and IsQuaternionCollection and IsAttributeStoringR rec() ) ); SetLeftActingDomain( HurwitzIntegers, Integers ); SetName( HurwitzIntegers, "HurwitzIntegers" ); SetString( HurwitzIntegers, "HurwitzIntegers" ); SetIsLeftActedOnByDivisionRing( HurwitzIntegers, false ); SetSize( HurwitzIntegers, infinity ); SetGeneratorsOfRing( HurwitzIntegers, AsList(QuaternionD4Basis)); SetGeneratorsOfLeftModule( HurwitzIntegers, AsList(QuaternionD4Basis) ); SetIsWholeFamily( HurwitzIntegers, false ); SetIsAssociative( HurwitzIntegers, false ); InstallMethod( Units, "For Hurwitz integers", [ IsHurwitzIntegers ], function(O) return Closure(Basis(O), \*); end); InstallMethod( IsHurwitzInt, "for Quaternions", [ IsQuaternion ], function(x) return ForAll(Coefficients(Basis(HurwitzIntegers), x), IsInt); end); InstallMethod( \in, "for integers", [ IsQuaternion, IsHurwitzIntegers ], 10000, function( n, Integers ) return IsHurwitzInt( n ); end ); InstallMethod( Basis, "for Hurwitz integers (delegate to `CanonicalBasis')", [ IsHurwitzIntegers ], CANONICAL_BASIS_FLAGS, CanonicalBasis ); InstallMethod( CanonicalBasis, "for Hurwitz integers", [ IsHurwitzIntegers ], function( HurwitzIntegers ) local B; B:= Objectify( NewType( FamilyObj( HurwitzIntegers ), IsFiniteBasisDefault and IsCanonicalBasis and IsQuaternionCollection and IsCanonicalBasisHurwitzIntegersRep ), rec() ); SetUnderlyingLeftModule( B, HurwitzIntegers ); SetIsIntegralBasis( B, true ); SetBasisVectors( B, Immutable( BasisVectors(QuaternionD4Basis))); # Return the basis. return B; end ); InstallMethod( Coefficients, "for the canonical basis of HurwitzIntegers", [ IsCanonicalBasisHurwitzIntegersRep, IsQuaternion ], 0, function( B, v ) return SolutionMat(List(B, ExtRepOfObj), ExtRepOfObj(v)); end ); # Icosian and Golden Field Tools InstallGlobalFunction( GoldenModSigma, function(q) # Check that q belongs to the quadratic field containing Sqrt(5). if not q in NF(5,[1,4]) then return fail; fi; # Compute the coefficients in the basis [1,(1-Sqrt(5))/2] and return the 1 coefficient. return Coefficients(Basis(NF(5,[1,4]), [1, (1-Sqrt(5))/2]), q)[1]; end ); BindGlobal( "IcosianH4Generators", Basis(QuaternionAlgebra(Field(Sqrt(5))), List([ [ 0, -1, 0, 0 ], [ 0, -1/2*E(5)^2-1/2*E(5)^3, 1/2, -1/2*E(5)-1/2*E(5)^4 ], [ 0, 0, -1, 0 ], [ -1/2*E(5)-1/2*E(5)^4, 0, 1/2, -1/2*E(5)^2-1/2*E(5)^3 ] ], x -> ObjByExtRep(FamilyObj(One(QuaternionAlgebra(Field(Sqrt(5))))),x) )) ); BindGlobal( "IcosianRing", Objectify( NewType( CollectionsFamily(FamilyObj(QuaternionAlgebra(Rationals))), IsIcosianRing and IsRingWithOne and IsQuaternionCollection and IsAttributeStoringRep ), rec() ) ); SetLeftActingDomain( IcosianRing, Integers ); SetName( IcosianRing, "IcosianRing" ); SetString( IcosianRing, "IcosianRing" ); SetIsLeftActedOnByDivisionRing( IcosianRing, false ); SetSize( IcosianRing, infinity ); SetGeneratorsOfRing( IcosianRing, AsList(IcosianH4Generators)); SetGeneratorsOfLeftModule( IcosianRing, AsList(IcosianH4Generators) ); SetIsWholeFamily( IcosianRing, false ); SetIsAssociative( IcosianRing, false ); InstallMethod( Units, "For Icosians", [ IsIcosianRing ], function(O) return Closure(Basis(O), \*); end); InstallMethod( IsIcosian, "for Quaternions", [ IsQuaternion ], function(x) return ForAll(Coefficients(Basis(IcosianRing), x), y -> ForAll(Coefficients(Basis(NF(5,[1,4]), [1, (1-Sqrt(5))/2]), y), IsInt) ); end); InstallMethod( \in, "for integers", [ IsQuaternion, IsIcosianRing ], 10000, function( n, Integers ) return IsIcosian( n ); end ); InstallMethod( Basis, "for Icosians (delegate to `CanonicalBasis')", [ IsIcosianRing ], CANONICAL_BASIS_FLAGS, CanonicalBasis ); InstallMethod( CanonicalBasis, "for Icosians", [ IsIcosianRing ], function( IcosianRing ) local B; B:= Objectify( NewType( FamilyObj( IcosianRing ), IsFiniteBasisDefault and IsCanonicalBasis and IsQuaternionCollection and IsCanonicalBasisIcosianRingRep ), rec() ); SetUnderlyingLeftModule( B, IcosianRing ); SetIsIntegralBasis( B, true ); SetBasisVectors( B, Immutable( BasisVectors(IcosianH4Generators))); # Return the basis. return B; end ); InstallMethod( Coefficients, "for the canonical basis of IcosianRing", [ IsCanonicalBasisIcosianRingRep, IsQuaternion ], 0, function( B, v ) return SolutionMat(List(B, ExtRepOfObj), ExtRepOfObj(v)); end ); # Function to construct an octonion algebra in a standard basis (i.e. e[1]*e[2] = e[4], and cycl InstallGlobalFunction( OctonionAlgebra, function( F ) local e, stored, filter, T, A; # Arguments checking if not IsField(F) then Error( "usage: OctonionAlgebra( <F> ) for a field <F>." ); fi; e:= One( F ); if e = fail then Error( "<F> must have an identity element" ); fi; # Generators in the right family may be already available. stored := GET_FROM_SORTED_CACHE( OctonionAlgebraData, [ Characteristic(F), FamilyObj( F function() # Construct a filter describing element properties, # which will be stored in the family. filter:= IsSCAlgebraObj and IsOctonion; # if HasIsAssociative( F ) and IsAssociative( F ) then # filter:= filter and IsAssociativeElement; # fi; T := [ [ [ [ 8 ], [ -1 ] ], [ [ 4 ], [ 1 ] ], [ [ 7 ], [ 1 ] ], [ [ 2 ], [ -1 ] ], [ [ 6 ], [ 1 ] ], [ [ 5 ], [ -1 ] ], [ [ 3 ], [ -1 ] ], [ [ 1 ], [ 1 ] ] ], [ [ [ 4 ], [ -1 ] ], [ [ 8 ], [ -1 ] ], [ [ 5 ], [ 1 ] ], [ [ 1 ], [ 1 ] ], [ [ 3 ], [ -1 ] ], [ [ 7 ], [ 1 ] ], [ [ 6 ], [ -1 ] ], [ [ 2 ], [ 1 ] ] ], [ [ [ 7 ], [ -1 ] ], [ [ 5 ], [ -1 ] ], [ [ 8 ], [ -1 ] ], [ [ 6 ], [ 1 ] ], [ [ 2 ], [ 1 ] ], [ [ 4 ], [ -1 ] ], [ [ 1 ], [ 1 ] ], [ [ 3 ], [ 1 ] ] ], [ [ [ 2 ], [ 1 ] ], [ [ 1 ], [ -1 ] ], [ [ 6 ], [ -1 ] ], [ [ 8 ], [ -1 ] ], [ [ 7 ], [ 1 ] ], [ [ 3 ], [ 1 ] ], [ [ 5 ], [ -1 ] ], [ [ 4 ], [ 1 ] ] ], [ [ [ 6 ], [ -1 ] ], [ [ 3 ], [ 1 ] ], [ [ 2 ], [ -1 ] ], [ [ 7 ], [ -1 ] ], [ [ 8 ], [ -1 ] ], [ [ 1 ], [ 1 ] ], [ [ 4 ], [ 1 ] ], [ [ 5 ], [ 1 ] ] ], [ [ [ 5 ], [ 1 ] ], [ [ 7 ], [ -1 ] ], [ [ 4 ], [ 1 ] ], [ [ 3 ], [ -1 ] ], [ [ 1 ], [ -1 ] ], [ [ 8 ], [ -1 ] ], [ [ 2 ], [ 1 ] ], [ [ 6 ], [ 1 ] ] ], [ [ [ 3 ], [ 1 ] ], [ [ 6 ], [ 1 ] ], [ [ 1 ], [ -1 ] ], [ [ 5 ], [ 1 ] ], [ [ 4 ], [ -1 ] ], [ [ 2 ], [ -1 ] ], [ [ 8 ], [ -1 ] ], [ [ 7 ], [ 1 ] ] ], [ [ [ 1 ], [ 1 ] ], [ [ 2 ], [ 1 ] ], [ [ 3 ], [ 1 ] ], [ [ 4 ], [ 1 ] ], [ [ 5 ], [ 1 ] ], [ [ 6 ], [ 1 ] ], [ [ 7 ], [ 1 ] ], [ [ 8 ], [ 1 ] ] ], 0, Zero(F) ]; # Construct the algebra. A:= AlgebraByStructureConstantsArg([ F, T, "e" ], filter ); SetFilterObj( A, IsAlgebraWithOne ); SetFilterObj( A, IsOctonionAlgebra ); return A; end ); A:= AlgebraWithOne( F, CanonicalBasis( stored ), "basis" ); SetGeneratorsOfAlgebra( A, GeneratorsOfAlgebraWithOne( A ) ); SetIsFullSCAlgebra( A, true ); SetFilterObj( A, IsOctonionAlgebra ); # Return the octonion algebra. return A; end ); InstallMethod( Trace, "for an octonion", [ IsOctonion and IsSCAlgebraObj ], oct -> 2*ExtRepOfObj(oct)[8] ); InstallMethod( Norm, "for an octonion", [ IsOctonion and IsSCAlgebraObj ], oct -> ExtRepOfObj(oct)*ExtRepOfObj(oct) ); InstallMethod( Norm, "for an octonion list", [ IsOctonionCollection ], function(vec) return Sum(List(vec, Norm) ); end ); InstallMethod( ComplexConjugate, "for an octonion", [ IsOctonion and IsSCAlgebraObj ], oct -> One(oct)*Trace(oct) - oct ); InstallMethod( RealPart, "for an octonion", [ IsOctonion and IsSCAlgebraObj ], oct -> (1/2)*Trace(oct)*One(oct) ); # Avoiding use of ImaginaryPart for octonions since the built in GAP quaternion version of this # InstallMethod( ImaginaryPart, # "for an octonion", # [ IsOctonion and IsSCAlgebraObj ], # oct -> oct - RealPart(oct) # ); # Octonion arithmetic tools BindGlobal( "OctonionE8Basis", Basis(OctonionAlgebra(Rationals), List( [[ -1/2, 0, 0, 0, 1/2, 1/2, 1/2, 0 ], [ -1/2, -1/2, 0, -1/2, 0, 0, -1/2, 0 ], [ 0, 1/2, 1/2, 0, -1/2, 0, -1/2, 0 ], [ 1/2, 0, -1/2, 1/2, 1/2, 0, 0, 0 ], [ 0, -1/2, 1/2, 0, -1/2, 0, 1/2, 0 ], [ 0, 1/2, 0, -1/2, 1/2, -1/2, 0, 0 ], [ -1/2, 0, -1/2, 1/2, -1/2, 0, 0, 0 ], [ 1/2, 0, 0, -1/2, 0, 1/2, 0, -1/2 ] ], x -> ObjByExtRep(FamilyObj(One(OctonionAlgebra(Rationals))),x) )) ); BindGlobal( "OctavianIntegers", Objectify( NewType( CollectionsFamily(FamilyObj(OctonionAlgebra(Rationals))), IsOctavianIntegers and IsRingWithOne and IsOctonionCollection and IsAttributeStoringRe rec() ) ); SetLeftActingDomain( OctavianIntegers, Integers ); SetName( OctavianIntegers, "OctavianIntegers" ); SetString( OctavianIntegers, "OctavianIntegers" ); SetIsLeftActedOnByDivisionRing( OctavianIntegers, false ); SetSize( OctavianIntegers, infinity ); SetGeneratorsOfRing( OctavianIntegers, AsList(OctonionE8Basis)); SetGeneratorsOfLeftModule( OctavianIntegers, AsList(OctonionE8Basis) ); SetIsWholeFamily( OctavianIntegers, false ); SetIsAssociative( OctavianIntegers, false ); InstallMethod( Units, "For octavian integers", [ IsOctavianIntegers ], function(O) return Closure(Basis(O), \*); end); InstallMethod( IsOctavianInt, "for Octonions", [ IsOctonion ], function(x) return ForAll(Coefficients(Basis(OctavianIntegers), x), IsInt); end); InstallMethod( \in, "for integers", [ IsOctonion, IsOctavianIntegers ], 10000, function( n, Integers ) return IsOctavianInt( n ); end ); InstallMethod( Basis, "for Octavian integers (delegate to `CanonicalBasis')", [ IsOctavianIntegers ], CANONICAL_BASIS_FLAGS, CanonicalBasis ); InstallMethod( CanonicalBasis, "for Octavian integers", [ IsOctavianIntegers ], function( OctavianIntegers ) local B; B:= Objectify( NewType( FamilyObj( OctavianIntegers ), IsFiniteBasisDefault and IsCanonicalBasis and IsOctonionCollection and IsCanonicalBasisOctavianIntegersRep ), rec() ); SetUnderlyingLeftModule( B, OctavianIntegers ); SetIsIntegralBasis( B, true ); SetBasisVectors( B, Immutable( BasisVectors(OctonionE8Basis))); # Return the basis. return B; end ); InstallMethod( Coefficients, "for the canonical basis of OctavianIntegers", [ IsCanonicalBasisOctavianIntegersRep, IsOctonion ], 0, function( B, v ) return SolutionMat(List(B, ExtRepOfObj), ExtRepOfObj(v)); end ); InstallMethod( \mod, "For an octonion integer", [IsOctonion, IsPosInt], 0, function(a,m) local coeffs; coeffs := Coefficients(Basis(OctavianIntegers), a); if not ForAll(coeffs, IsInt) then return fail; fi; return LinearCombination(Basis(OctavianIntegers), coeffs mod m); end ); # Potentially replace the function below with a method. # InstallMethod( OctonionToRealVector, # "For an octonion basis and vector", # [ IsBasis, IsRowVector ], 0, # function(basis, x) # if IsHomogeneousList(Flat(AsList(Basis), x)) and # IsOctonionCollection(x) # then # return Flat(List(x, y -> Coefficients(basis, y)) ); # fi; # return fail; # end ); InstallGlobalFunction( OctonionToRealVector, function(arg, x) # In the case of an octonion basis return the concatenated octonion basis expansion. if IsBasis(arg) and IsOctonionCollection(UnderlyingLeftModule(arg)) and IsOctonionCol return Concatenation(List(x, y -> Coefficients(arg, y)) ); fi; return fail; end ); InstallMethod( Coefficients, "For an octonion lattice basis and an octonion vector", [ IsOctonionLatticeBasis, IsOctonionCollection ], 0, function(basis, x) local L; L := UnderlyingLeftModule(basis); if x in L then # return OctonionToRealVector(UnderlyingLeftModule(basis), x); return SolutionMat(LLLReducedBasisCoefficients(L), OctonionToRealVector((UnderlyingOctonionRingBasis(L)), x)); fi; return fail; end ); InstallGlobalFunction( RealToOctonionVector, function(arg, x) local n, temp; # In the case of an octonion basis convert each length of 8 into an octonion, # Check length of coefficient vector. if IsBasis(arg) and IsOctonionCollection(UnderlyingLeftModule(arg)) then if Length(x) mod 8 = 0 and IsHomogeneousList(x) then n := Length(x)/8; temp := List([1..n], m -> x{[(m-1)*8+1 .. m*8]} );; return List(temp, y -> LinearCombination(arg, y) ); fi; fi; return fail; end ); InstallGlobalFunction( VectorToIdempotentMatrix, function(x) local temp; if not IsHomogeneousList(x) or not IsAssociative(x) or not (IsCyc(x[1]) or IsQuaternion(x[ return fail; fi; if IsAssociative(x) then temp := TransposedMat([ComplexConjugate(x)])*[x]; return temp/Trace(temp ); fi; return fail; end ); InstallGlobalFunction( WeylReflection, function(r,x) local R; R := VectorToIdempotentMatrix(r ); if R = fail or not IsHomogeneousList(Flat([r,x])) then return fail; fi; return x - 2*x*R; end ); # Jordan Algebra Tools InstallMethod( Rank, "for a Jordan Algebra", [ IsJordanAlgebra ], J -> JordanRank(J) ); InstallMethod( JordanRank, "for a Jordan algebra element", [ IsJordanAlgebraObj ], j -> JordanRank(FamilyObj(j)!.fullSCAlgebra) ); InstallMethod( Rank, "for a Jordan algebra element", [ IsJordanAlgebraObj ], j -> JordanRank(j) ); InstallMethod( JordanDegree, "for a Jordan algebra element", [ IsJordanAlgebraObj ], j -> JordanDegree(FamilyObj(j)!.fullSCAlgebra) ); InstallMethod( Degree, "for a Jordan Algebra", [ IsJordanAlgebra ], J -> JordanDegree(J) ); InstallMethod( Degree, "for a Jordan algebra element", [ IsJordanAlgebraObj ], j -> JordanDegree(j) ); InstallMethod( Trace, "for a Jordan algebra element", [ IsJordanAlgebraObj and IsSCAlgebraObj ], # j -> (Rank(j)/Dimension(FamilyObj(j)!.fullSCAlgebra))*Trace(AdjointMatrix(Basis(Fa j -> ExtRepOfObj(j)*JordanBasisTraces(FamilyObj(j)!.fullSCAlgebra) ); InstallMethod( Norm, "for a Jordan algebra element", [ IsJordanAlgebraObj and IsSCAlgebraObj ], j -> Trace(j^2)/2 ); InstallGlobalFunction( GenericMinimalPolynomial, function(x) local p, prx, p1xr, r, j, qjx; p := [-Trace(x)]; p1xr := [-Trace(x)]; r := 1; repeat r := r + 1; Append(p1xr, [-Trace(x^r)] ); prx := (1/r)*(p1xr[r] + Sum(List([1..r-1], j -> p1xr[r-j]*p[j] )) ); Append(p, [prx] ); until r = Rank(x ); p := Reversed(p ); Append(p, [1] ); return p; end ); InstallMethod( Determinant, "for a Jordan algebra element", [ IsJordanAlgebraObj and IsSCAlgebraObj ], j -> ValuePol(GenericMinimalPolynomial(j), 0)*(-1)^Rank(j) ); InstallMethod( JordanAdjugate, "for a Jordan algebra element", [ IsJordanAlgebraObj ], function(j) return (-1)^(1+Rank(j))*ValuePol(ShiftedCoeffs(GenericMinimalPolynomia ); InstallMethod( IsPositiveDefinite, "for a Jordan algebra element", [ IsJordanAlgebraObj ], function(j) local temp; temp := GenericMinimalPolynomial(j ); if 0 in temp then return false; fi; temp := Reversed(temp ); temp := List([0..Rank(j)], n -> temp[n+1]*(-1)^n > 0 ); if Set(temp) = [true] then return true; fi; return false; end ); # Function to construct basis matrices for a Hermitian simple Euclidean Jordan algebra. InstallGlobalFunction( HermitianJordanAlgebraBasis, function(rho, comp_alg_basis) local d, C, F, peirce, conj, mat, frame, realbasis; # Ensure that the rank and degree are correct. if not (IsInt(rho) and rho > 1 and IsBasis(comp_alg_basis)) then return fail; fi; d := Length(comp_alg_basis); if (not d in [1,2,4,8]) or (d = 8 and rho > 3) then return fail; fi; # Record the composition algebra over F. C := UnderlyingLeftModule(comp_alg_basis); F := LeftActingDomain(C); # Require that F is either integers or a field of characteristic zero. if not (IsIntegers(F) or (IsField(F) and Characteristic(F) = 0)) then return fail; fi; # It is possible that the d = 1 or 2 cases do not involve quaternions or octonion SCAlgebra objects if not (IsOctonionCollection(C) or IsQuaternionCollection(C)) then # Only real and complex cases remain, which must be quadratic extensions of some number field. if d > 2 then return fail; fi; # Rule out subfields of the rationals for d = 2: if d = 2 and Set(comp_alg_basis, x -> RealPart(x) = x ) = [true] then return fail; fi; fi; # Define a function to construct a single entry Hermitian matrix. mat := function(n,x) local temp; if Length(n) <> 2 then return fail; fi; temp := Zero(x)*IdentityMat( rho ); temp[n[1]][n[2]] := x; temp[n[2]][n[1]] := ComplexConjugate( x ); return temp; end; # Construct the diagonal matrices. frame := Concatenation(List(IdentityMat(rho), x -> List([One(C)], r -> DiagonalMat(x)*r)) ) # Construct the off-diagonal matrices. peirce := List(Combinations([1..rho],2), n -> List(comp_alg_basis, x -> mat(n,x)) ); # Return the matrices. return Concatenation(frame, Concatenation(peirce) ); end ); # Function to convert a Hermitian matrix to a vector, or coefficients of a vector, in a Jordan alg InstallGlobalFunction( HermitianMatrixToJordanCoefficients, function(mat, comp_alg_ local temp, rho, d, i, basis; # Verify that the input is a Hermitian matrix. if not IsMatrix(mat) and mat = TransposedMat(ComplexConjugate(mat)) then return fail; fi; # Ensure that the second input is a basis. if not IsBasis(comp_alg_basis) then return fail; fi; # Record basic parameters. basis := comp_alg_basis; rho := Length(DiagonalOfMat(mat) ); d := Size(basis); # Define a temporary list of coefficients. temp := []; # Determine the coefficients due to the diagonal components of the matrix. for i in [1..rho] do if IsQuaternionCollection(comp_alg_basis) or IsOctonionCollection(comp_alg_basis) th Append(temp, [Trace(mat[i][i])/2] ); elif IsCyclotomicCollection(comp_alg_basis) then Append(temp, [RealPart(mat[i][i])]); else Display("Here"); return fail; fi; od; # Find the off-diagonal coefficients next. for i in Combinations([1..rho],2) do # if not (IsQuaternionCollection(comp_alg_basis) or IsOctonionCollection(comp_alg_bas # Append(temp, Coefficients(Basis(Rationals,[1]), mat[i[1]][i[2]]) ); # else # Append(temp, Coefficients(basis, mat[i[1]][i[2]]) ); # fi; Append(temp, Coefficients(basis, mat[i[1]][i[2]]) ); od; # Return the coefficients. return temp; end ); # Function to convert a Hermitian matrix into a Jordan algebra vector. InstallGlobalFunction( HermitianMatrixToJordanVector, function(mat, J) local temp; # Verify that the second argument is a Jordan algebra with an off-diagonal basis defined. if not (IsJordanAlgebra(J) and HasJordanOffDiagonalBasis(J)) then return fail; fi; # Verify that the matrix entries belong to the algebra spanned by the off-diagonal basis. if not IsHomogeneousList(Flat([mat, JordanOffDiagonalBasis(J)])) then return fail; fi; # Compute the coefficients, if possible. temp := HermitianMatrixToJordanCoefficients(mat, JordanOffDiagonalBasis(J) ); if temp = fail then return temp; fi; # Return the coefficients in J-vector form. return LinearCombination(Basis(J), temp ); end ); # Function to construct Jordan algebra of Hermitian type. InstallGlobalFunction( HermitianSimpleJordanAlgebra, function(rho, comp_alg_basis, F local jordan_basis, C, K, T, temp, coeffs, algebra, filter, n, m, z, l; # Ensure inputs are correct by computing basis vectors: if Length(F) > 1 then return fail; fi; jordan_basis := HermitianJordanAlgebraBasis(rho, comp_alg_basis ); if jordan_basis = fail then return jordan_basis; fi; # Record the composition algebra over F. C := UnderlyingLeftModule(comp_alg_basis); K := LeftActingDomain(C); if Length(F) = 0 and IsSubset(Rationals, K) then K := Rationals; fi; # Ensure that the optional field argument contains the left acting domain of the basis. if Length(F) = 1 then F := F[1]; if not (IsField(F) or IsIntegers(F)) then return fail; elif IsField(F) and not IsSubset(F, K) then return fail; fi; K := F; fi; # Define an empty structure constants table. T := EmptySCTable(Size(jordan_basis), Zero(K) ); # Compute the structure constants. for n in [1..Size(jordan_basis)] do for m in [1..Size(jordan_basis)] do z := (1/2)*(jordan_basis[n]*jordan_basis[m] + jordan_basis[m]*jordan_basis[n] ); # z := (jordan_basis[n]*jordan_basis[m] + jordan_basis[m]*jordan_basis[n] ); temp := HermitianMatrixToJordanCoefficients(z, comp_alg_basis ); coeffs := []; for l in [1..Size(jordan_basis)] do if temp[l] <> 0 then Append(coeffs, [temp[l], l] ); fi; od; SetEntrySCTable( T, n, m, coeffs ); od; od; # Construct the algebra. filter:= IsSCAlgebraObj and IsJordanAlgebraObj; algebra := AlgebraByStructureConstantsArg([K, T], filter ); SetFilterObj( algebra, IsJordanAlgebra ); SetFilterObj( algebra, IsAlgebraWithOne); # Assign various attributes to the algebra. SetJordanRank( algebra, rho ); SetJordanDegree( algebra, Length(comp_alg_basis) ); SetJordanMatrixBasis( algebra, jordan_basis ); SetJordanOffDiagonalBasis( algebra, comp_alg_basis ); SetJordanHomotopeVector( algebra, One(algebra) ); SetJordanBasisTraces( algebra, List(Basis(algebra), j -> (Rank(j)/Dimension(FamilyObj(j)!.fullSCAlgebra))*Trace(AdjointMatrix(Basis(Fam ); return algebra; end ); InstallGlobalFunction( JordanSpinFactor, function(gram_mat) local result, T, n, m, z, temp, coeffs, filter; if not IsMatrix(gram_mat) or Inverse(gram_mat) = fail or gram_mat <> TransposedMat(gram_mat) Display("Usage: JordanSpinFactor(G) requires <G> to be a positive definite symmetric matrix. return fail; fi; result := rec( ); result.F := Field(Flat(gram_mat) ); result.rho := 2; result.d := DimensionsMat(gram_mat)[1]-1; # Construct the algebra. T := EmptySCTable(result.d + 2, Zero(0) ); SetEntrySCTable(T, 1, 1, [1, 1] ); for m in [2..result.d + 2] do SetEntrySCTable(T, m, 1, [1, m] ); SetEntrySCTable(T, 1, m, [1, m] ); od; for n in [2..result.d + 2] do for m in [2..result.d + 2] do SetEntrySCTable( T, n, m, [gram_mat[n-1][m-1], 1] ); od; od; filter:= IsSCAlgebraObj and IsJordanAlgebraObj; result.algebra := AlgebraByStructureConstantsArg([result.F, T], filter ); SetFilterObj( result.algebra, IsJordanAlgebra ); SetFilterObj( result.algebra, IsAlgebraWithOne); SetJordanRank( result.algebra, result.rho ); SetJordanDegree( result.algebra, result.d ); SetJordanHomotopeVector( result.algebra, One(result.algebra) ); SetJordanBasisTraces( result.algebra, List(Basis(result.algebra), j -> (Rank(j)/Dimension(FamilyObj(j)!.fullSCAlgebra))*Trace(AdjointMatrix(Basis(Fam ); return result.algebra; end ); InstallMethod( JordanAlgebraGramMatrix, "for a Jordan algebra", [ IsJordanAlgebra ], j -> List(Basis(j), x -> List(Basis(j), y -> Trace(x*y))) ); InstallGlobalFunction( JordanHomotope , function(ring, u, label...) local result, temp, filter, T, n, m, z, l, coeffs; if not IsJordanAlgebra(ring) then return fail; fi; result := rec( ); result.rho := Rank(ring ); result.d := Degree(ring ); result.F := LeftActingDomain(ring ); T := EmptySCTable(Dimension(ring), Zero(result.F) ); for n in Basis(ring) do for m in Basis(ring) do z := n*(u*m) + (n*u)*m - u*(n*m ); temp := Coefficients(Basis(ring), z ); coeffs := []; for l in [1..Dimension(ring)] do if temp[l] <> Zero(temp[l]) then Append(coeffs, [temp[l], l] ); fi; od; SetEntrySCTable( T, Position(Basis(ring), n), Position(Basis(ring), m), coeffs ); od; od; filter:= IsSCAlgebraObj and IsJordanAlgebraObj; if Length(label) > 0 and IsString(label[1]) then result.algebra := AlgebraByStructureConstantsArg([result.F, T, label[1]], filter ); else result.algebra := AlgebraByStructureConstantsArg([result.F, T], filter ); fi; SetFilterObj( result.algebra, IsJordanAlgebra ); if Inverse(u) <> fail then SetFilterObj( result.algebra, IsAlgebraWithOne); fi; SetJordanRank( result.algebra, result.rho ); SetJordanDegree( result.algebra, result.d ); if HasJordanMatrixBasis( result.algebra) then SetJordanMatrixBasis( result.algebra, JordanMatrixBasis(ring) ); fi; if HasJordanOffDiagonalBasis(result.algebra) then SetJordanOffDiagonalBasis( result.algebra, JordanOffDiagonalBasis(ring) ); fi; SetJordanHomotopeVector( result.algebra, u ); SetJordanBasisTraces( result.algebra, List(Basis(result.algebra), j -> (Rank(j)/Dimension(FamilyObj(j)!.fullSCAlgebra))*Trace(AdjointMatrix(Basis(Fam ); return result.algebra; end ); InstallGlobalFunction( SimpleEuclideanJordanAlgebra, function(rho, d, args...) local temp, F; temp := rec( ); if not (IsInt(d) and IsInt(rho)) then return fail; fi; if rho < 2 then return fail; fi; if rho > 2 and not d in [1,2,4,8] then return fail; fi; if d = 8 and rho > 3 then return fail; fi; if rho = 2 then if Length(args) = 0 then return JordanSpinFactor(IdentityMat(d+1) ); elif IsMatrix(args[1]) and DimensionsMat(args[1]) = [d+1, d+1] and TransposedMat(args[1] return JordanSpinFactor(args[1] ); elif d in [1,2,4,8] and IsBasis(args[1]) and Size(args[1]) = d then return HermitianSimpleJordanAlgebra(rho, args[1] ); else Display("Usage: SimpleEuclideanJordanAlgebra(2, d [, args]) where <args> is either empty, a s return fail; fi; fi; if Length(args) = 0 then if d = 8 then return HermitianSimpleJordanAlgebra(rho, Basis(OctonionAlgebra(Rationals)) ); elif d = 4 then return HermitianSimpleJordanAlgebra(rho, Basis(QuaternionAlgebra(Rationals)) ); elif d = 2 then return HermitianSimpleJordanAlgebra(rho, Basis(CF(4), [1, E(4)]) ); elif d = 1 then return HermitianSimpleJordanAlgebra(rho, Basis(Rationals, [1]) ); fi; elif IsBasis(args[1]) and Size(args[1]) = d then return HermitianSimpleJordanAlgebra(rho, args[1] ); else return fail; fi; end ); # Albert Algebra tools InstallGlobalFunction( AlbertAlgebra, function( F ) local e, i, j, k, jordan_basis, stored, filter, T, A; # Arguments checking if not IsField(F) then Error( "usage: AlbertAlgebra( <F> ) for a field <F>." ); fi; e:= One( F ); if e = fail then Error( "<F> must have an identity element" ); fi; # Generators in the right family may be already available. stored := GET_FROM_SORTED_CACHE( AlbertAlgebraData, [ Characteristic(F), FamilyObj( F ) ] function() filter:= IsSCAlgebraObj and IsJordanAlgebraObj and IsAlbertAlgebraObj; T := [ [ [ [ 26, 27 ], [ 1, 1 ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ 24 ], [ -1/2 ] ], [ [ 20 ], [ -1/2 ] ], [ [ 23 ], [ -1/2 ] ], [ [ 18 ], [ 1/2 ] ], [ [ 22 ], [ -1/2 ] ], [ [ 21 ], [ 1/2 ] ], [ [ 19 ], [ 1/2 ] ], [ [ 17 ], [ -1/2 ] ], [ [ 16 ], [ -1/2 ] ], [ [ 12 ], [ 1/2 ] ], [ [ 15 ], [ 1/2 ] ], [ [ 10 ], [ -1/2 ] ], [ [ 14 ], [ 1/2 ] ], [ [ 13 ], [ -1/2 ] ], [ [ 11 ], [ -1/2 ] ], [ [ 9 ], [ -1/2 ] ], [ [ ], [ ] ], [ [ 1 ], [ 1/2 ] ], [ [ 1 ], [ 1/2 ] ] ], [ [ [ 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[ [ 24 ], [ 1/2 ] ], [ [ ], [ ] ] ], [ [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ 9 ], [ 1/2 ] ], [ [ 10 ], [ 1/2 ] ], [ [ 11 ], [ 1/2 ] ], [ [ 12 ], [ 1/2 ] ], [ [ 13 ], [ 1/2 ] ], [ [ 14 ], [ 1/2 ] ], [ [ 15 ], [ 1/2 ] ], [ [ 16 ], [ 1/2 ] ], [ [ 17 ], [ 1/2 ] ], [ [ 18 ], [ 1/2 ] ], [ [ 19 ], [ 1/2 ] ], [ [ 20 ], [ 1/2 ] ], [ [ 21 ], [ 1/2 ] ], [ [ 22 ], [ 1/2 ] ], [ [ 23 ], [ 1/2 ] ], [ [ 24 ], [ 1/2 ] ], [ [ 25 ], [ 1 ] ], [ [ ], [ ] ], [ [ ], [ ] ] ], [ [ [ 1 ], [ 1/2 ] ], [ [ 2 ], [ 1/2 ] ], [ [ 3 ], [ 1/2 ] ], [ [ 4 ], [ 1/2 ] ], [ [ 5 ], [ 1/2 ] ], [ [ 6 ], [ 1/2 ] ], [ [ 7 ], [ 1/2 ] ], [ [ 8 ], [ 1/2 ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ 17 ], [ 1/2 ] ], [ [ 18 ], [ 1/2 ] ], [ [ 19 ], [ 1/2 ] ], [ [ 20 ], [ 1/2 ] ], [ [ 21 ], [ 1/2 ] ], [ [ 22 ], [ 1/2 ] ], [ [ 23 ], [ 1/2 ] ], [ [ 24 ], [ 1/2 ] ], [ [ ], [ ] ], [ [ 26 ], [ 1 ] ], [ [ ], [ ] ] ], [ [ [ 1 ], [ 1/2 ] ], [ [ 2 ], [ 1/2 ] ], [ [ 3 ], [ 1/2 ] ], [ [ 4 ], [ 1/2 ] ], [ [ 5 ], [ 1/2 ] ], [ [ 6 ], [ 1/2 ] ], [ [ 7 ], [ 1/2 ] ], [ [ 8 ], [ 1/2 ] ], [ [ 9 ], [ 1/2 ] ], [ [ 10 ], [ 1/2 ] ], [ [ 11 ], [ 1/2 ] ], [ [ 12 ], [ 1/2 ] ], [ [ 13 ], [ 1/2 ] ], [ [ 14 ], [ 1/2 ] ], [ [ 15 ], [ 1/2 ] ], [ [ 16 ], [ 1/2 ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ ], [ ] ], [ [ 27 ], [ 1 ] ] ], 1, Zero(F) ]; # Construct the algebra. A:= AlgebraByStructureConstantsArg([F, T, "i1", "i2", "i3", "i4", "i5", "i6", "i7", "i8", "j1", "j2", "j3", "j4", "j5", "j6", "j7", "j8", "k1", "k2", "k3", "k4", "k5", "k6", "k7", "k8", "ei", "ej", "ek"], filter ); SetFilterObj( A, IsAlgebraWithOne ); SetFilterObj( A, IsJordanAlgebra ); SetJordanRank( A, 3 ); SetJordanDegree( A, 8 ); SetJordanOffDiagonalBasis( A, Basis(OctonionAlgebra(Rationals)) ); SetJordanHomotopeVector( A, One(A) ); SetJordanBasisTraces( A, List(Basis(A), j -> (Rank(j)/Dimension(FamilyObj(j)!.fullSCAlgebra))*Trace(AdjointMatrix(Basis(Fam ); return A; end ); A:= AlgebraWithOne( F, CanonicalBasis( stored ), "basis" ); SetGeneratorsOfAlgebra( A, GeneratorsOfAlgebraWithOne( A ) ); SetIsFullSCAlgebra( A, true ); SetFilterObj( A, IsJordanAlgebra ); SetFilterObj( A, IsAlgebraWithOne); SetJordanRank( A, 3 ); SetJordanDegree( A, 8 ); SetJordanOffDiagonalBasis( A, Basis(OctonionAlgebra(Rationals)) ); SetJordanHomotopeVector( A, One(A) ); SetJordanBasisTraces( A, List(Basis(A), j -> (Rank(j)/Dimension(FamilyObj(j)!.fullSCAlgebra))*Trace(AdjointMatrix(Basis(Fam ); jordan_basis := HermitianJordanAlgebraBasis(3, CanonicalBasis(OctonionAlgebra(Ratio e := jordan_basis{[1..3]}; i := jordan_basis{[20..27]}; j := ComplexConjugate(jordan_basis{[12..19]}); k := jordan_basis{[4..11]}; jordan_basis := Concatenation([i,j,k,e]); SetJordanMatrixBasis( A, jordan_basis ); return A; end ); InstallGlobalFunction( HermitianMatrixToAlbertVector, function(mat) local temp; if not IsMatrix(mat) or not DimensionsMat(mat) = [3,3] or not IsSubset(OctonionAlgebra(Rat return fail; fi; if ComplexConjugate(TransposedMat(mat)) <> mat then return fail; fi; temp := HermitianMatrixToJordanCoefficients(mat, Basis(OctonionAlgebra(Rationals))) temp := Concatenation([temp{[20..27]}, -temp{[12..18]}, temp{[19]}, temp{[4..11]}, tem return LinearCombination(Basis(AlbertAlgebra(Rationals)), temp); end); InstallGlobalFunction( AlbertVectorToHermitianMatrix, function(vec) if not IsAlbertAlgebraObj(vec) then return fail; fi; return LinearCombination(JordanMatrixBasis(AlbertAlgebra(Rationals)), ExtRepOfObj( end); # See Faraut and Koranyi p. 32 InstallMethod( JordanQuadraticOperator, "for a Jordan algebra element", [ IsJordanAlgebraObj ], function(j) return 2*AdjointMatrix(CanonicalBasis(FamilyObj(j)!.fullSCAlgebra), j)^2 - AdjointMa end); InstallMethod( JordanQuadraticOperator, "for a pair of Jordan algebra elements", [ IsJordanAlgebraObj, IsJordanAlgebraObj ], function(j, k) return 2*j*(j*k) - (j^2)*k; end); InstallMethod( JordanTripleSystem, "for three Jordan algebra elements", [IsJordanAlgebraObj, IsJordanAlgebraObj, IsJordanAlgebraObj], {x,y,z} -> x*(y*z) + (x*y)*z - (x*z)*y ); # T-Design Tools InstallGlobalFunction( JacobiPolynomial, function(k, a, b) local temp, a1, a2, a3, a4, n, x; if not IsInt(k) and k > -1 then return fail; fi; if not (IsPolynomial(a) or (IsRat(a) and a > -1)) then return fail; fi; if not (IsPolynomial(b) or (IsRat(b) and a > -1)) then return fail; fi; n := k - 1; a1 := 2*(n+1)*(n+a+b+1)*(2*n+a+b ); a2 := (2*n+a+b+1)*(a^2 - b^2 ); a3 := (2*n + a + b)*(2*n + a + b + 1)*(2*n + a + b + 2 ); a4 := 2*(n+a)*(n+b)*(2*n+a+b+2 ); x := [0,1]; if k = 0 then return [1]; elif k = -1 then return [0]; elif k = 1 then return (1/2)*[a-b,(a+b+2)]; fi; return ProductCoeffs([a2/a1, a3/a1], JacobiPolynomial(k-1,a,b))-(a4/a1)*JacobiPolyn end ); InstallGlobalFunction( Q_k_epsilon, function(k, epsilon, rank, degree, x) local temp, p, poch, N, m; if k = 0 and epsilon = 0 then return 1+0*x; fi; m := degree/2; N := rank*m; p := ValuePol(JacobiPolynomial(k, N-m-1, m-1+epsilon), 2*x - 1 ); poch := function(a,n) if n = 1 then return a; elif n = 0 then return 1; elif n < 0 then return 0; fi; return Product(List([1..n], b -> a + b -1) ); end; temp := poch(N, k + epsilon - 1)*poch(N-m, k)*(2*k + N + epsilon - 1 ); temp := temp/(Factorial(k)*poch(m,k+epsilon) ); return temp*p/Value(p, [x], [1] ); end ); InstallGlobalFunction( R_k_epsilon, function(k, epsilon, rank, degree, x) local temp, n; temp := 0*x; for n in [0..k] do temp := temp + Q_k_epsilon(n, epsilon, rank, degree, x ); od; return temp; end ); InstallGlobalFunction( JordanDesignByParameters, function(rank, degree) local obj, F, x; # Check that the inputs match a Jordan primitive idempotent space if not IsInt(rank) or rank < 2 then return fail; fi; if rank > 2 and not degree in [1,2,4,8] then return fail; fi; if degree = 8 and rank > 3 then return fail; fi; # Create the object obj := Objectify(NewType(NewFamily( "Design"), IsJordanDesign and IsComponentObjectRep SetFilterObj(obj, IsAttributeStoringRep ); # Assign rank and degree attributes. SetJordanDesignRank(obj, rank ); SetJordanDesignDegree(obj, degree ); # Assign Spherical or Projective filters. if rank = 2 then SetFilterObj(obj, IsSphericalJordanDesign ); fi; if degree in [1,2,4,8] then SetFilterObj(obj, IsProjectiveJordanDesign ); fi; return obj; end ); InstallMethod( PrintObj, "for a design", [ IsJordanDesign ], function(x) local text; Print( "<design with rank ", JordanDesignRank(x), " and degree ", JordanDesignDegree(x), ">" ) end ); InstallMethod(JordanDesignQPolynomials, "Generic method for designs", [ IsJordanDesign ], function(D) local x, temp; x := Indeterminate(Rationals, "x" ); temp := function(k) if IsInt(k) and k > -1 then return CoefficientsOfUnivariatePolynomial((Q_k_epsilon(k, 0, JordanDesignRank(D), Jo fi; return fail; end; return temp; end ); InstallMethod( JordanDesignConnectionCoefficients, "Generic method for designs", [ IsJordanDesign ], function(D) local temp; temp := function(s) local x, Q, V, basis, mat, k, i; x := Indeterminate(Rationals, "x" ); Q := List([0..s], i -> Q_k_epsilon(i,0, JordanDesignRank(D), JordanDesignDegree(D), x) ); V := VectorSpace(Rationals, Q ); basis := Basis(V, Q ); mat := []; for k in [0..s] do Append(mat, [ Coefficients(basis, x^k) ] ); od; return mat; end; return temp; end ); InstallMethod( JordanDesignAddAngleSet, "for designs", [ IsJordanDesign, IsList ], function(D, A) if not (ForAll(A, IsCyc) and ForAll(A, x -> ComplexConjugate(x) = x) and ForAll(A, x -> not IsRat(x) or (x < 1 and x >= 0))) then return fail; fi; SetJordanDesignAngleSet(D, Set(A) ); SetFilterObj(D, IsJordanDesignWithAngleSet ); # Assign Positive Indicator Coefficients filter if applicable. if [true] = Set(JordanDesignNormalizedIndicatorCoefficients(D), x -> x > 0) then SetFilterObj(D, IsJordanDesignWithPositiveIndicatorCoefficients ); fi; return D; end ); InstallGlobalFunction( JordanDesignByAngleSet, function(rank, degree, A) local obj, F, x; obj := JordanDesignByParameters(rank, degree ); if obj = fail then return obj; fi; # Test the angle set: if not (ForAll(A, IsCyc) and ForAll(A, x -> ComplexConjugate(x) = x) and ForAll(A, x -> not IsRat(x) or (x < 1 and x >= 0))) then return fail; fi; # Assign angle set. SetJordanDesignAngleSet(obj, Set(A) ); SetFilterObj(obj, IsJordanDesignWithAngleSet ); # Assign Positive Indicator Coefficients filter if applicable. if [true] = Set(JordanDesignNormalizedIndicatorCoefficients(obj), x -> x > 0) then SetFilterObj(obj, IsJordanDesignWithPositiveIndicatorCoefficients ); fi; return obj; end ); InstallMethod( PrintObj, "for a design with angle set", [ IsJordanDesignWithAngleSet ], function(x) local text; Print( "<design with rank ", JordanDesignRank(x), ", degree ", JordanDesignDegree(x), ", and end ); InstallMethod( JordanDesignNormalizedAnnihilatorPolynomial, "generic method for designs", [ IsJordanDesignWithAngleSet ], function(D) local x, F, A; A := JordanDesignAngleSet(D ); x := Indeterminate(Field(A), "x" ); F := Product(List(A, a -> (x - a)/(1-a)) ); return CoefficientsOfUnivariatePolynomial(F ); end ); InstallMethod( JordanDesignNormalizedIndicatorCoefficients, "generic method for designs", [ IsJordanDesignWithAngleSet ], function(D) local x, r, d, Q, F, V, basis; r := JordanDesignRank(D ); d := JordanDesignDegree(D ); x := Indeterminate(Field(JordanDesignAngleSet(D)), "x" ); Q := k -> Q_k_epsilon(k, 0, r, d, x ); F := ValuePol(JordanDesignNormalizedAnnihilatorPolynomial(D), x ); V := VectorSpace(Field(JordanDesignAngleSet(D)), List([0..Degree(F)], Q) ); basis := Basis(V, List([0..Degree(F)], Q) ); return Coefficients(basis, F ); end ); InstallMethod( JordanDesignSpecialBound, "generic method for designs", [ IsJordanDesignWithAngleSet and IsJordanDesignWithPositiveIndicatorCoefficients ], function(D) if Filtered(JordanDesignNormalizedIndicatorCoefficients(D), x -> x < 0) <> [] then return fail; fi; return 1/JordanDesignNormalizedIndicatorCoefficients(D)[1]; end ); InstallMethod( JordanDesignAddCardinality, "for designs with angle sets", [ IsJordanDesignWithAngleSet, IsInt ], function(D, v) local obj; SetJordanDesignCardinality(D, v ); SetFilterObj(D, IsJordanDesignWithCardinality ); if JordanDesignSpecialBound(D) = JordanDesignCardinality(D) then SetFilterObj(D, IsSpecialBoundJordanDesign ); JordanDesignStrength(D ); fi; return D; end ); InstallMethod( PrintObj, "for a design with cardinality", [ IsJordanDesignWithCardinality ], function(x) Print( "<design with rank ", JordanDesignRank(x), ", degree ", JordanDesignDegree(x), ", car end ); InstallMethod( JordanDesignStrength, "method for designs with positive indicator coefficients", [ IsJordanDesignWithPositiveIndicatorCoefficients and IsJordanDesignWithCardinality function(D) local s, i, t, e; s := Size(JordanDesignAngleSet(D) ); for i in [0..s] do if JordanDesignIndicatorCoefficients(D)[i+1] = 1 then t := s + i; fi; od; SetFilterObj(D, IsJordanDesignWithStrength ); if 0 in JordanDesignAngleSet(D) then e := 1; else e := 0; fi; # Check for tightness, etc if t = 2*s - e then SetFilterObj(D, IsTightJordanDesign ); return t; fi; if t >= 2*s - 2 then SetFilterObj(D, IsAssociationSchemeJordanDesign ); return t; fi; return t; end ); InstallMethod( JordanDesignAnnihilatorPolynomial, "generic method for designs", [ IsJordanDesignWithAngleSet and IsJordanDesignWithCardinality ], function(D) return JordanDesignCardinality(D)*JordanDesignNormalizedAnnihilatorPolynomial(D ); end ); InstallMethod( JordanDesignIndicatorCoefficients, "generic method for designs", [ IsJordanDesignWithAngleSet and IsJordanDesignWithCardinality ], function(D) return JordanDesignCardinality(D)*JordanDesignNormalizedIndicatorCoefficients(D ); end ); InstallMethod( PrintObj, "for a design with angle set and strength", [IsJordanDesignWithAngleSet and IsJordanDesignWithStrength], function(x) local text; Print( "<", JordanDesignStrength(x), "-design with rank ", JordanDesignRank(x), ", degree " end ); InstallMethod( PrintObj, "for a tight design", [IsTightJordanDesign], function(x) Print( "<Tight ", JordanDesignStrength(x), "-design with rank ", JordanDesignRank(x), ", de end ); InstallMethod( JordanDesignSubdegrees, "method for a regular scheme design", [ IsRegularSchemeJordanDesign and IsJordanDesignWithCardinality and IsJordanDesignWit function(D) local rank, degree, v, A, f, s, mat, vec, i; --> -------------------- --> maximum size reached --> -------------------- [ Dauer der Verarbeitung: 0.11 Sekunden (vorverarbeitet) ] |
2026-04-02