division algebra
Noun
Meaning
(algebra) A linear algebra such that its non-zero vectors form a multiplicative group.
Synonym: associative division algebra
Hypernyms: associative algebra, linear algebra, division ring, vector space
Hyponyms: field, quaternions, complex numbers, reals
(algebra) An algebra over a field such that every non-zero element of it has a multiplicative inverse. (It is not required to have a unity element.)
Hypernyms: algebra over a field, ring, vector space
Hyponym: octonions
Synonyms
Examples
A central simple algebra over K is a matrix algebra over a (finite dimensional) division algebra with center K. For example, the central simple algebras over the reals are matrix algebras over either the reals or the quaternions.
By the Artin–Wedderburn theorem (specifically, Wedderburn's part), CSAs are all matrix algebras over a division algebra, and thus the quaternions are the only non-trivial division algebra over the reals.
For example: * Every real Banach algebra which is a division algebra is isomorphic to the reals, the complexes, or the quaternions.
Hence, the only complex Banach algebra which is a division algebra is the complexes.
Let A be a complex unital Banach algebra in which every non-zero element x is invertible (a division algebra).
Quaternions form a division algebra —every non-zero element has an inverse—whereas Pauli matrices do not.