Commutant

Commutant

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. 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.

Properties

  • S' = S''' = S''''' - A commutant is its own bicommutant.
  • S'' = S'''' = S'''''' - A bicommutant is its own bicommutant.

See also


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