Birational properties of tangent to the identity germs without non-degenerate singular directions

Abstract

We provide a family of isolated tangent to the identity germs $f:({\mathbb{C}}^3,0)\to ({\mathbb{C}}^3,0)$ which possess only degenerate characteristic directions, and for which the lift of $f$ to any modification (with suitable properties) has only degenerate characteristic directions. This is in sharp contrast with the situation in dimension $2$, where any isolated tangent to the identity germ $f$ admits a modification where the lift of $f$ has a non-degenerate characteristic direction. We compare this situation with the resolution of singularities of the infinitesimal generator of $f$, showing that this phenomenon is not related to the non-existence of complex separatrices for vector fields of Gomez-Mont and Luengo. Finally, we describe the set of formal $f$-invariant curves, and the associated parabolic manifolds, using the techniques recently developed by López-Hernanz, Raissy, Ribón, Sanz Sánchez, Vivas.

42 pages, 3 figures