Ditkin set

In mathematics, a Ditkin set, introduced by (Ditkin 1939), is a closed subset of the circle such that a function f vanishing on the set can be approximated by functions φ_nf with φ vanishing in a neighborhood of the set.

References

• Ditkin, V. (1939), "On the structure of ideals in certain normed rings", Uchenye Zapiski Moskov. Gos. Univ. Matematika, 30: 83–130, MR 0002012