Dynamics of generic 1-parameter perturbations of a vector field with a singular point of codimension k

Abstract

The paper describes the bifurcation diagram of germs of generic $1$-parameter families of complex vector fields $\dot z = ω_ε(z)$ on $\mathbb{C}$, unfolding a singular point of multiplicity $k+1$: $ω_0= z^{k+1} +o(z^{k+1})$. As a preparatory step, the bifurcation diagram of the family of vector fields $\dot z = z^{k+1}-ε$ over $\mathbb{CP}^1$ is given, through a description of its associated translation surface as a star shaped domain (a straightening coordinate, a.k.a.\ time coordinate, of a vector field defines a translation surface structure on the complement of the singularities). In this article, we define a notion of generic families of vector fields $\dot z = ω_ε(z)$, and classify them up to conjugacy by a holomorphic change of coordinate and parameter. A description of the modulus space and several (almost) unique normal forms are provided. Then, we describe an analogue of the star shaped domain for these generic vector fields, that we call the geometric model and which allows to describe the local bifurcation diagram for generic families of vector fields in fine details and compare it with that of the simple vector field $\dot z = z^{k+1}-ε$ restricted to $B(0,r)$.