Horn maps of holomorphic functions locally pseudo-conjugate on their local parabolic basin

Abstract: The lifted horn map $h$ of a holomorphic function $f$ with a simple parabolic point at $z_0$ is well known to be a local conjugacy complete invariant at $z_0$; this is a classical result proved independently by \'Ecalle, Voronin, Martinet and Ramis. Landford and Yampolski have shown that, if two functions $f_1, f_2$ with simple parabolic points at $z_1, z_2$ are globally conjugate over their immediate parabolic basins, with the conjugacy and its inverse continuous at $z_1$, resp. $z_2$, their horn maps must be equal as analytic ramified coverings. In this article, we introduce a notion of local conjugacy over immediate parabolic basins, and show that two functions $f_1, f_2$ with simple parabolic points are locally conjugate over parabolic basins (without the hypothesis of continuity) if and only if the non-lifted horn maps $\mathbf{h}_i$ are equivalent as ramified coverings. This result is a first step to understand better invariant classes by parabolic renormalization.