Linearization of holomorphic germs with resonant linear part

We study the linearization problem of germs of holomorphic diffeomorphisms with resonant linear part. The formal linearization requires in general an infinite number of algebraic relations to be satisfied by the coefficients of the power series defining the holomorphic germ. For a fixed germ, the linearizing mappings are not unique, but the existence of a finite jet with a formal divergent linearization but no convergent one forces all the other linearizing mappings to be diverging. We consider also polynomial families formally conjugated to a fixed resonant linear part. Then all the elements of the family are holomorphically linearizable, or we are in the precedent diverging situation for all but an exceptional set of parameter values of zero $\Gamma$-capacity. In the case of maximal non-trivial resonance we prove the optimality of Bruno condition.