augmentation ideal
英[ˌɔ:gmenˈteɪʃən aiˈdiəl]美[ˌɔɡmɛnˈteʃən aɪˈdiəl]
In algebra, an augmentation ideal is an ideal that can be defined in any group ring. If G is a group and R a commutative ring, there is a ring homomorphism \varepsilon, called the augmentation map, from the group ring