simple algebra
Noun
Meaning
simple algebra (plural simple algebras)
(algebra) An algebra that contains no nontrivial proper (two-sided) ideals and whose multiplication operation is not zero (i.e., there exist a and b such that ab ≠ 0).
Examples
A closer non-commutative analog are central simple algebras (CSAs) – ring extensions over a field, which are simple algebra (no non-trivial 2-sided ideals, just as for a field) and where the center of the ring is exactly the field.
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.
For example, the only finite field extension of the real numbers is the complex numbers, while the quaternions are a central simple algebra over the reals, and all CSAs over the reals are Brauer equivalent to the reals or the quaternions.
In this section, a central simple algebra is assumed to have finite dimension.
Since the center of a simple k-algebra is a field, any simple k-algebra is a central simple algebra over its center.
The Skolem–Noether theorem states any automorphism of a central simple algebra is inner.