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Maths - Derivation of Octonion Tables

As explaned on this page we can build up these division algebras into more and more complex algebras by combining these in different ways using the Kronecker product and then , this will allow us to generate all of the Clifford algebras.

For example we could generate the quaternions from C⊗C

Table for: octonion

(C⊗C)⊗C

a*bb.eb.e1b.e2b.e3b.e4b.e5b.e6b.e7
a.eee1e2e3e4e5e6e7
a.e1e1-ee3-e2e5-e4e7 -e6
a.e2e2-e3-ee1e6-e7 -e4e5
a.e3e3e2-e1-ee7e6 -e5 -e4
a.e4e4-e5-e6-e7-ee1e2e3
a.e5e5e4-e7e6-e1-ee3 -e2
a.e6e6e7e4-e5-e2-e3 -ee1
a.e7e7-e6e5e4-e3e2 -e1 -e

analysing commutivity: table does not commute: for example: e1*e2 != e2*e1

analysing associativity: table does not associate, for example, (e4* e1)* e2=-e5* e2=e7 is not equal to e4*(e1* e2)=e4*e3=-e7

how these results were generated.

compare with fano plane:

.

 

 

a*b
b.1 b.e1 b.e2 b.e3 b.e4 b.e5 b.e6 b.e7
a.1 1 e1 e2 e3 e4 e5 e6 e7
a.e1 e1 -1 -e3 e2 -e5 e4 e7 -e6
a.e2 e2 e3 -1 -e1 -e6 -e7 e4 e5
a.e3 e3 -e2 e1 -1 -e7 e6 -e5 e4
a.e4 e4 e5 e6 e7 -1 -e1 -e2 -e3
a.e5 e5 -e4 e7 -e6 e1 -1 e3 -e2
a.e6 e6 -e7 -e4 e5 e2 -e3 -1 e1
a.e7 e7 e6 -e5 -e4 e3 e2 -e1 -1

Table for: octonion

C⊗(C⊗C)

a*bb.eb.e1b.e2b.e3b.e4b.e5b.e6b.e7
a.eee1e2e3e4e5e6e7
a.e1e1-ee3-e2e5-e4e7-e6
a.e2e2-e3-ee1e6-e7-e4e5
a.e3e3e2-e1-ee7e6-e5-e4
a.e4e4-e5-e6e7-ee1e2-e3
a.e5e5e4-e7-e6-e1-ee3e2
a.e6e6-e7e4-e5-e2e3-ee1
a.e7e7e6e5e4-e3-e2-e1-e

analysing commutivity: table does not commute: for example: e1*e2 != e2*e1

analysing associativity: table does not associate, for example, (e2* e4)* e1=e6* e1=-e7 is not equal to e2*(e4* e1)=e2*-e5=e7

how these results were generated.

.

a*b
b.1 b.e1 b.e2 b.e3 b.e4 b.e5 b.e6 b.e7
a.1 1 e1 e2 e3 e4 e5 e6 e7
a.e1 e1 -1 -e3 e2 -e5 e4 e7 -e6
a.e2 e2 e3 -1 -e1 -e6 -e7 e4 e5
a.e3 e3 -e2 e1 -1 -e7 e6 -e5 e4
a.e4 e4 e5 e6 e7 -1 -e1 -e2 -e3
a.e5 e5 -e4 e7 -e6 e1 -1 e3 -e2
a.e6 e6 -e7 -e4 e5 e2 -e3 -1 e1
a.e7 e7 e6 -e5 -e4 e3 e2 -e1 -1

From Fano Plane

a*b
b.1 b.e1 b.e2 b.e3 b.e4 b.e5 b.e6 b.e7
a.1 1 e1 e2 e3 e4 e5 e6 e7
a.e1 e1 -1 e4 e7 -e2 e6 -e5 -e3
a.e2 e2 -e4 -1 e5 e1 -e3 e7 -e6
a.e3 e3 -e7 -e5 -1 e6 e2 -e4 e1
a.e4 e4 e2 -e1 -e6 -1 e7 e3 -e5
a.e5 e5 -e6 e3 -e2 -e7 -1 e1 e4
a.e6 e6 e5 -e7 e4 -e3 -e1 -1 e2
a.e7 e7 e3 e6 -e1 e5 -e4 -e2 -1

 


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see also:

If you are interested in this, there is a very good paper by John Baez

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