Nilpotent algebra


In mathematics, specifically in ring theory, a nilpotent algebra over a commutative ring is an algebra over a commutative ring, in which for some positive integer n every product containing at least n elements of the algebra is zero. The concept of a nilpotent Lie algebra has a different definition, which depends upon the Lie bracket. Another possible source of confusion in terminology is the quantum nilpotent algebra, a concept related to quantum groups and Hopf algebras.

Formal definition

An associative algebra over a commutative ring is defined to be a nilpotent algebra if and only if there exists some positive integer such that for all in the algebra. The smallest such is called the index of the algebra. In the case of a non-associative algebra, the definition is that every different multiplicative association of the elements is zero.

Nil algebra

An algebra in which every element of the algebra is nilpotent is called a nil algebra.
Nilpotent algebras are trivially nil, whereas nil algebras may not be nilpotent, as each element being nilpotent does not force products of distinct elements to vanish.