Octonion Algebra Is Frobenius In Just One Way
Linear operators over a 8-dimensional vector space representing octonnion algebra
Ref:
We need the Axiom LinearOperator library.
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)library CARTEN ARITY CMONAL CPROP CLOP CALEY
CartesianTensor is now explicitly exposed in frame initial
CartesianTensor will be automatically loaded when needed from
/var/aw/var/LatexWiki/CARTEN.NRLIB/CARTEN
Arity is now explicitly exposed in frame initial
Arity will be automatically loaded when needed from
/var/aw/var/LatexWiki/ARITY.NRLIB/ARITY
ClosedMonoidal is now explicitly exposed in frame initial
ClosedMonoidal will be automatically loaded when needed from
/var/aw/var/LatexWiki/CMONAL.NRLIB/CMONAL
ClosedProp is now explicitly exposed in frame initial
ClosedProp will be automatically loaded when needed from
/var/aw/var/LatexWiki/CPROP.NRLIB/CPROP
ClosedLinearOperator is now explicitly exposed in frame initial
ClosedLinearOperator will be automatically loaded when needed from
/var/aw/var/LatexWiki/CLOP.NRLIB/CLOP
CaleyDickson is now explicitly exposed in frame initial
CaleyDickson will be automatically loaded when needed from
/var/aw/var/LatexWiki/CALEY.NRLIB/CALEY
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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-- subscript
macro sb == subscript
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 ℂ == CaleyDickson
Type: Void
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macro ℚ == Expression Integer
Type: Void
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ℒ := ClosedLinearOperator(OVAR ['0,'1,'2,'3,'4,'5,'6,'7], ℚ)
Type: Type
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ⅇ:List ℒ := basisOut()
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ⅆ:List 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
Now generate structure constants for Octonion 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.
Split-complex, co-quaternions and split-octonions can be specified by Caley-Dickson parameters
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--q0:=sb('q,[0])
q0:=1 -- not split-complex
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--q1:=sb('q,[1])
q1:=1 -- not co-quaternion
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q2:=sb('q,[2])
Type: Symbol
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--q2:=1 -- split-octonion
QQ := ℂ(ℂ(ℂ(ℚ,'i,q0),'j,q1),'k,q2);
Type: Type
Basis: Each B.i is a octonion number
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B:List QQ := map(x +-> hyper x,1$SQMATRIX(dim,ℚ)::List List ℚ)
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-- Multiplication table:
M:Matrix QQ := matrix [[B.i*B.j for i in 1..dim] for j in 1..dim]
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-- Function to divide the matrix entries by a basis element
S(y) == map(x +-> real real real(x/y),M)
Type: Void
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-- The result is a nested list
ѕ :=map(S,B)::List List List ℚ;
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Compiling function S with type CaleyDickson(CaleyDickson(
CaleyDickson(Expression(Integer),i,1),j,1),k,q[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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arity Y
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matrix [[(ⅇ.i*ⅇ.j)/Y for i in 1..dim] for j in 1..dim]
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 [[retract((ⅇ.i * ⅇ.j)/Ũ) for j in 1..dim] for i in 1..dim]
Type: Expression(Integer)
General Solution
We may consider the problem where multiplication Y is given,
and look for all associative scalar products
This problem can be solved using linear algebra.
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)expose MCALCFN
MultiVariableCalculusFunctions is now explicitly exposed in frame
initial
J := jacobian(ravel ω,concat map(variables,ravel U)::List Symbol);
Type: Matrix(Expression(Integer))
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u := transpose matrix [concat map(variables,ravel U)::List Symbol];
Type: Matrix(Polynomial(Integer))
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J::OutputForm * u::OutputForm = 0
Type: Equation(OutputForm
?)
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nrows(J),ncols(J)
Type: Tuple(PositiveInteger
?)
The matrix J
transforms the coefficients of the tensor
into coefficients of the tensor . We are looking for
the general linear family of tensors such that
J
transforms into for any such .
If the null space of the J
matrix is not empty we can use
the basis to find all non-trivial solutions for U:
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Ñ:=nullSpace(J);
Type: List(Vector(Expression(Integer)))
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ℰ:=map((x,y)+->x=y, concat
map(variables,ravel U), entries Σ(sb('p,[i])*Ñ.i, i,1..#Ñ) )
>> Error detected within library code:
reducing over an empty list needs the 3 argument form
This defines a family of Frobenius algebras:
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zero? eval(ω,ℰ)
There are 12 exposed and 6 unexposed library operations named eval
having 2 argument(s) but none was determined to be applicable.
Use HyperDoc Browse, or issue
)display op eval
to learn more about the available operations. Perhaps
package-calling the operation or using coercions on the arguments
will allow you to apply the operation.
Cannot find a definition or applicable library operation named eval
with argument type(s)
ClosedLinearOperator(OrderedVariableList([0,1,2,3,4,5,6,7]),Expression(Integer))
Variable(ℰ)
Perhaps you should use "@" to indicate the required return type,
or "$" to specify which version of the function you need.
The pairing is necessarily diagonal!
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Ų:ℒ := eval(U,ℰ)
There are 12 exposed and 6 unexposed library operations named eval
having 2 argument(s) but none was determined to be applicable.
Use HyperDoc Browse, or issue
)display op eval
to learn more about the available operations. Perhaps
package-calling the operation or using coercions on the arguments
will allow you to apply the operation.
Cannot find a definition or applicable library operation named eval
with argument type(s)
ClosedLinearOperator(OrderedVariableList([0,1,2,3,4,5,6,7]),Expression(Integer))
Variable(ℰ)
Perhaps you should use "@" to indicate the required return type,
or "$" to specify which version of the function you need.
The scalar product must be non-degenerate:
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Ů:=determinant [[retract((ⅇ.i * ⅇ.j)/Ų) for j in 1..dim] for i in 1..dim]
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
>> Error detected within library code:
failed
Definition 3
Co-pairing
Solve the Snake Relation as a system of linear equations.
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Um:=matrix [[(ⅇ.i*ⅇ.j)/Ų for i in 1..dim] for j in 1..dim]
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
0 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
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mU:=transpose inverse map(retract,Um)
>> Error detected within library code:
failed
Check "dimension" and the snake relations.
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d:ℒ:=
Ω /
X /
Ų
2
0 +
- --
0 2
+
arity warning: ----
2
0 +
- --
0 2
+
2
+ 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
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test
( I Ω ) /
( Ų I ) = I
Type: Boolean
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test
( Ω I ) /
( I Ų ) = I
There are no library operations named Ω
Use HyperDoc Browse or issue
)what op Ω
to learn if there is any operation containing " Ω " in its name.
Cannot find a definition or applicable library operation named Ω
with argument type(s)
ClosedLinearOperator(OrderedVariableList([0,1,2,3,4,5,6,7]),Expression(Integer))
Perhaps you should use "@" to indicate the required return type,
or "$" to specify which version of the function you need.
Definition 4
Co-algebra
Compute the "three-point" function and use it to define co-multiplication.
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W:=(Y,I)/Ų
3
+ 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
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λ:=(Ω,I,Ω)/(I,W,I)
4
+ +
- --
+ 4
+
arity warning: ----
5
0 +
- --
0 4
+
>> System error:
Heap exhausted (no more space for allocation).
There are still 807796736 bytes available; the request was for 1073741840 bytes.
PROCEED WITH CAUTION.
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test
( I Ω ) /
( Y I ) = λ
2
+ +
- --
+ 2
+
arity warning: ----
3
0 +
- --
0 2
+
Type: Boolean
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test
( Ω I ) /
( I Y ) = λ
There are no library operations named Ω
Use HyperDoc Browse or issue
)what op Ω
to learn if there is any operation containing " Ω " in its name.
Cannot find a definition or applicable library operation named Ω
with argument type(s)
ClosedLinearOperator(OrderedVariableList([0,1,2,3,4,5,6,7]),Expression(Integer))
Perhaps you should use "@" to indicate the required return type,
or "$" to specify which version of the function you need.
Frobenius Condition
Octonion algebra fails the Frobenius Condition!
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H :=
Y /
λ
2
+ 0
-- -
+ 0
arity warning: ----
+ 0
- -
+ 0
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Hr := (λ,I)/(I,Y)
2
+ +
- --
+ 2
+
arity warning: ----
3
0 +
- --
0 2
+
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test(Hr = H )
Type: Boolean
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Hl := (I,λ)/(Y,I);
2
+ +
- --
+ 2
+
arity warning: ----
3
0 +
- --
0 2
+
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test( Hl = H )
Type: Boolean
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test( Hr = Hl )
Type: Boolean
Perhaps this is not too surprising since Octonion algebra is
non-associative. Nevertheless Octonions are "Frobenius" in a more
general sense because there is a non-degenerate associative
pairing.
i = Unit of the algebra
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i:=ⅇ.1
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test
i /
λ = Ω
0 0
- -
+ 0
arity warning: ---
+ 0
- -
+ 0
Type: Boolean
Handle and handle element
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Φ:ℒ :=
λ /
X /
Y
2
0 +
- --
0 2
+
arity warning: ----
2
0 +
- --
0 2
+
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Φ1:= i /
Φ
0 +
- -
+ +
arity warning: ----
2
0 +
- --
0 +
Definition 5
Co-unit
i
U
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ι:ℒ:=
( i I ) /
( Ų )
+ 0
-- -
2 0
+
arity warning: ----
2
+ 0
-- -
2 0
+
Y=U
ι
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test
Y /
ι = Ų
Type: Boolean
For example:
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ex1:=[q[2]=1,p[1]=1]
Type: List(Equation(Polynomial(Integer)))
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Ų0:ℒ :=eval(Ų,ex1)
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Ω0:ℒ :=eval(Ω,ex1)$ℒ
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λ0:ℒ :=eval(λ,ex1)$ℒ
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H0:ℒ :=eval(H,ex1)$ℒ