… × ) gives the left-hand side a group structure, the group ring R[Γ] (or its spectrum) is a group
… that S is a free OK-module, and hence aI[n+1] is a free submodule, consequently, a · z ∈ aI[…

… First we recall a coherent sheaf F is CM (Cohen-Macaulay) if all its stalks Fp are CM
modules. A scheme X is CM if the structure sheaf OX is CM. Projective CM varieties can be …