  Let X be a smooth projective scheme of dimension d >= 1 over the field k, and
let C be an indecomposable coherent sheaf on X. Then there is an
Auslander-Reiten sequence in the category of quasi-coherent sheaves on X, with
C as right hand end term.
  The left hand end term of the sequence can be computed. It is the (d-1)'st
syzygy in a minimal injective resolution of C, tensor the dualizing sheaf of X.
