Semi-simple algebra

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with respect to a radical

An algebra which is an -semi-simple ring (see Semi-simple ring). In some classes of algebras and for a suitable choice of the radical , it is possible to describe the structure of a semi-simple algebra (see Classical semi-simple ring; Alternative rings and algebras; Jordan algebra; Lie algebra, semi-simple).

By a semi-simple algebra one frequently understands a finite-dimensional algebra over a field which is a direct sum of simple algebras.


By Wedderburn's theorem (cf. Wedderburn–Artin theorem), an Artinian algebra with Jacobson radical zero is a finite direct sum of simple algebras.


[a1] P.M. Cohn, "Algebra" , 2 , Wiley (1989) pp. Chapt. 5
How to Cite This Entry:
Semi-simple algebra. L.A. Skornyakov (originator), Encyclopedia of Mathematics. URL:
This text originally appeared in Encyclopedia of Mathematics - ISBN 1402006098