composition algebras over
There are 7 non-isomorphic composition algebras over , first 4 division algebras
and secondly3 split algebras
.
- 1.
The real numbers .
- 2.
The complex numbers
.
- 3.
The Hamiltonians (also known as the quaternions) .
- 4.
The octonions (also known as the Cayley or Cayley-Dickson algebra) .
- 5.
The exchange algebra: .
- 6.
matrices over : .
- 7.
The cross-product of -matrices over : .
The proof can be seen as a consquence of a theorem of Hurwitz and a theorem of Jacobson.In reality various authors contributed to the solution including Albert, Dickson andKaplansky.