Commutant

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Not to be confused with commutator or commutator subgroup.

In algebra, the commutant of a subset S of a semigroup (such as an algebra or a group) A is the subset S′ of elements of A commuting with every element of S.[1] In other words,

S'=\{x\in A: sx=xs\ \mbox{for}\ \mbox{every}\ s\in S\}.

S′ forms a subsemigroup. This generalizes the concept of centralizer in group theory.

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