Automatic differentiability and characterization of cocycles of holomorphic flows

In this paper we prove that cocycles of holomorphic flows on do-mains in the complex plane are automatically differentiable with respect to the flow parameter, and their derivatives are holomorphic functions. We use this result to show that, on simply connected domains, an additive cocycle is a coboundary if and only if this cocycle vanishes at the fixed point of the flow.