English
For a set s ⊆ A, the centralizer centralizes s together with its star-closure; it forms a StarSubalgebra of A consisting of elements commuting with every element of s ∪ s*.
Русский
Централизатор s ∪ s* образует звездную подсалгебру, состоящую из элементов, коммутирующих с каждым элементом s ∪ s*.
LaTeX
$$def centralizer (s : Set A) : StarSubalgebra R A$$
Lean4
/-- The centralizer, or commutant, of the star-closure of a set as a star subalgebra. -/
def centralizer (s : Set A) : StarSubalgebra R A
where
toSubalgebra := Subalgebra.centralizer R (s ∪ star s)
star_mem' := Set.star_mem_centralizer