In mathematical group theory, a subgroup of a group is termed a special abelian subgroup or SA-subgroup if the centralizer of any nonidentity element in the subgroup is precisely the subgroup. Equivalently, an SA subgroup is a centrally closed abelian subgroup.
Any SA subgroup is a maximal abelian subgroup, that is, it is not properly contained in another abelian subgroup. For a CA group, the SA subgroups are precisely the maximal abelian subgroups.
SA subgroups are known for certain characters associated with them termed exceptional characters.
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