Elementary amenable group
- Elementary amenable group
In mathematics, a group is called elementary amenable if it can be built up from finite groups and abelian groups by a sequence of simple operations that result in amenable groups when applied to amenable groups. Since finite groups and abelian groups are amenable, every elementary amenable group is amenable - however, the converse is not true.
Formally, the class of elementary amenable groups is the smallest subclass of the class of all groups that satisfies the following conditions:
*it contains all finite and all abelian groups
*if "G" is in the subclass and "H" is isomorphic to "G", then "H" is in the subclass
*it is closed under the operations of taking subgroups, forming quotients, and forming extensions
*it is closed under directed unions.
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