Commutant

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In algebra, the commutant of a subset S of an algebra A over a field K is the subset S′ of elements of A commuting with every element of S. In other words,

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

S′ forms a subalgebra. This is analogous to the concept of a centralizer in group theory.

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