The Pauli Algebra Cl(3) Is Frobenius In Many Ways
Linear operators over a 8-dimensional vector space representing Pauli algebra
Ref:
We need the Axiom LinearOperator library.
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(1) -> )library CARTEN ARITY CMONAL CPROP CLOP CALEY
CartesianTensor is now explicitly exposed in frame initial
CartesianTensor will be automatically loaded when needed from
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Arity is now explicitly exposed in frame initial
Arity will be automatically loaded when needed from
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ClosedMonoidal is now explicitly exposed in frame initial
ClosedMonoidal will be automatically loaded when needed from
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ClosedProp is now explicitly exposed in frame initial
ClosedProp will be automatically loaded when needed from
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ClosedLinearOperator is now explicitly exposed in frame initial
ClosedLinearOperator will be automatically loaded when needed from
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CaleyDickson is now explicitly exposed in frame initial
CaleyDickson will be automatically loaded when needed from
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Use the following macros for convenient notation
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-- summation
macro Σ(x,i,n)==reduce(+,[x for i in n])
Type: Void
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-- list
macro Ξ(f,i,n)==[f for i in n]
Type: Void
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-- subscript and superscripts
macro sb == subscript
Type: Void
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macro sp == superscript
Type: Void
𝐋 is the domain of 8-dimensional linear operators over the rational functions ℚ (Expression Integer), i.e. ratio of polynomials with integer coefficients.
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dim:=8
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macro ℒ == List
Type: Void
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macro ℂ == CaleyDickson
Type: Void
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macro ℚ == Expression Integer
Type: Void
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𝐋 := ClosedLinearOperator(OVAR ['1,'i,'j,'k,'ij,'ik,'jk,'ijk], ℚ)
Type: Type
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𝐞:ℒ 𝐋 := basisOut()
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𝐝:ℒ 𝐋 := basisIn()
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I:𝐋:=[1] -- identity for composition
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X:𝐋:=[2,1] -- twist
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V:𝐋:=ev(1) -- evaluation
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Λ:𝐋:=co(1) -- co-evaluation
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equate(eq)==map((x,y)+->(x=y),ravel lhs eq, ravel rhs eq);
Type: Void
Now generate structure constants for Pauli Algebra
The basis consists of the real and imaginary units. We use quaternion multiplication to form the "multiplication table" as a matrix. Then the structure constants can be obtained by dividing each matrix entry by the list of basis vectors.
The Pauli Algebra as Cl(3)
Basis: Each B.i is a Clifford number
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q0:=sp('i,[2])
Type: Symbol
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q1:=sp('j,[2])
Type: Symbol
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q2:=sp('k,[2])
Type: Symbol
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QQ:=CliffordAlgebra(3,ℚ,matrix [[q0,0,0],[0,q1,0],[0,0,q2]])
Type: Type
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B:ℒ QQ := [monomial(1,[]),monomial(1,[1]),monomial(1,[2]),monomial(1,[3]),monomial(1,[1,2]),monomial(1,[1,3]),monomial(1,[2,3]),monomial(1,[1,2,3])]
Type: List(CliffordAlgebra
?(3,
Expression(Integer),
[[i[;2],
0,
0],
[0,
j[;2],
0],
[0,
0,
k[;2]]]))
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M:Matrix QQ := matrix Ξ(Ξ(B.i*B.j, i,1..dim), j,1..dim)
Type: Matrix(CliffordAlgebra
?(3,
Expression(Integer),
[[i[;2],
0,
0],
[0,
j[;2],
0],
[0,
0,
k[;2]]]))
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S(y) == map(x +-> coefficient(recip(y)*x,[]),M)
Type: Void
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ѕ :=map(S,B)::ℒ ℒ ℒ ℚ
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Compiling function S with type CliffordAlgebra(3,Expression(Integer)
,[[i[;2],0,0],[0,j[;2],0],[0,0,k[;2]]]) -> Matrix(Expression(
Integer))
Type: List(List(List(Expression(Integer))))
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-- structure constants form a tensor operator
Y := Σ(Σ(Σ(ѕ(i)(k)(j)*𝐞.i*𝐝.j*𝐝.k, i,1..dim), j,1..dim), k,1..dim)
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matrix Ξ(Ξ((𝐞.i*𝐞.j)/Y, i,1..dim), j,1..dim)
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XY := X/Y;
Units
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e:=𝐞.1; i:=𝐞.2; j:=𝐞.3; k:=𝐞.4; ij:=𝐞.5; ik:=𝐞.6; jk:=𝐞.7; ijk:=𝐞.8;
Multiplication of arbitrary quaternions and
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a:=Σ(sb('a,[i])*𝐞.i, i,1..dim)
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b:=Σ(sb('b,[i])*𝐞.i, i,1..dim)
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(a*b)/Y
Multiplication is Associative
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test(
( I Y ) / _
( Y ) = _
( Y I ) / _
( Y ) )
Type: Boolean
A scalar product is denoted by the (2,0)-tensor
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U:=Σ(Σ(script('u,[[],[i,j]])*𝐝.i*𝐝.j, i,1..dim), j,1..dim)
Definition 1
We say that the scalar product is associative if the tensor
equation holds:
Y = Y
U U
In other words, if the (3,0)-tensor:
(three-point function) is zero.
Using the LinearOperator domain in Axiom and some carefully chosen symbols we can easily enter expressions that are both readable and interpreted by Axiom as "graphical calculus" diagrams describing complex products and compositions of linear operators.
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ω:𝐋 := _
( Y I ) / _
U - _
( I Y ) / _
U;
Definition 2
An algebra with a non-degenerate associative scalar product
is called a [Frobenius Algebra]?.
The Cartan-Killing Trace
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Ú:=
( Y Λ ) / _
( Y I ) / _
V
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Ù:=
( Λ Y ) / _
( I Y ) / _
V
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test(Ù=Ú)
Type: Boolean
forms a non-degenerate associative scalar product for Y
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Ũ := Ù
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test
( Y I ) /
Ũ =
( I Y ) /
Ũ
Type: Boolean
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determinant Ξ(Ξ(retract((𝐞.i * 𝐞.j)/Ũ), j,1..dim), i,1..dim)
Type: Expression(Integer)
General Solution
Frobenius Form (co-unit)
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d:=ε1*𝐝.1+εi*𝐝.2+εj*𝐝.3+εk*𝐝.4+εij*𝐝.5+εik*𝐝.6+εjk*𝐝.7+εijk*𝐝.8
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Ų:= Y/d
In general the pairing is not symmetric!
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u1:=matrix Ξ(Ξ(retract((𝐞.i 𝐞.j)/Ų), i,1..dim), j,1..dim)
Type: Matrix(Expression(Integer))
The scalar product must be non-degenerate:
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--Ů:=determinant u1
--factor(numer Ů)/factor(denom Ů)
1
Cartan-Killing is a special case
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ck:=solve(equate(Ũ=Ų),[ε1,εi,εj,εk,εij,εik,εjk,εijk]).1
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Compiling function equate with type Equation(ClosedLinearOperator(
OrderedVariableList([1,i,j,k,ij,ik,jk,ijk]),Expression(Integer)))
-> List(Equation(Expression(Integer)))
Type: List(Equation(Expression(Integer)))
Frobenius scalar product of "vector" quaternions and
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a:=sb('a,[1])*i+sb('a,[2])*j+sb('a,[3])*k
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b:=sb('b,[1])*i+sb('b,[2])*j+sb('b,[3])*k
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(a,a)/Ų
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(b,b)/Ų
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(a,b)/Ų
Definition 3
Co-scalar product
Solve the Snake Relation as a system of linear equations.
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mU:=inverse matrix Ξ(Ξ(retract((𝐞.i*𝐞.j)/Ų), i,1..dim), j,1..dim);
Type: Union(Matrix(Expression(Integer)),...)
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Ω:=Σ(Σ(mU(i,j)*(𝐞.i*𝐞.j), i,1..dim), j,1..dim);
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ΩX:=Ω/X;
The common demoninator is
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--squareFreePart factor denom Ů / squareFreePart factor numer Ů
matrix Ξ(Ξ(numer retract(Ω/(𝐝.i*𝐝.j)), i,1..dim), j,1..dim)
Type: Matrix(SparseMultivariatePolynomial
?(Integer,
Kernel(Expression(Integer))))
Check "dimension" and the snake relations.
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O:𝐋:= Ω / Ų
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test
( I ΩX ) /
( Ų I ) = I
Type: Boolean
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test
( ΩX I ) /
( I Ų ) = I
Type: Boolean
Cartan-Killing co-scalar
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eval(Ω,ck)
Definition 4
Co-algebra
Compute the "three-point" function and use it to define co-multiplication.
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W:= (Y I) / Ų;
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λ:= _
( I ΩX ) / _
( Y I );
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test
( ΩX I ) /
( I Y ) = λ
Type: Boolean
Cartan-Killing co-multiplication
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eval(λ,ck)
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test
e /
λ = ΩX
Type: Boolean