Work

The is an from class functions on a subgroup H with support on a subset K of H to on a group G (, 6.1). It was introduced by Dade () as a generalisation and simplification of an isometry used by in their proof of the , and was used by in his revision of the character theory of the odd order theorem.

is a relating the numbers of characters of blocks of a finite group to the numbers of characters of blocks of local .