Unbounded derivations

In this note we discuss various extensions of a normal * derivation of a uniformly hyperfinite C^*-algebra. Various approximation theorems are employed to show when said extensions generate automorphism groups of the C^*-algebra. We characterize the "maximal" extension of Sakai and Powers as a graph limit and show when this extension is the closure of the given derivation. We also discuss an identity obeyed by the resolvent of a derivation.