Construction of idempotent 2-cocycles.

Let f : G × G ⟶ L be a weak 2-cocycle, where L / K is a finite Galois field extension with Galois group G , and A f = ( L / K , f ) be the associated weak crossed product K -algebra. We associate a partition of G to A f and construct idempotent 2-cocycles of A f . [ABSTRACT FROM AUTHOR]