On the topological invariance of the algebraic multiplicity of holomorphic foliations
Resumo: In this talk, I will address one of the most basic and fundamental problems in the theory of foliations and ODEs, the topological invariance of the algebraic multiplicity of a holomorphic foliation. For instance, I will present an adapted version of A'Campo-Lê's Theorem for foliations, i.e., the algebraic multiplicity equal to one is a topological invariant in dimension two. This result is further generalized to higher dimensions under mild conditions; consequently, we prove that saddle-nodes are topological invariant. We prove that the algebraic multiplicity is a topological invariant in several classes of foliations that contain, for instance, the generalized curves and the foliations of the second type.
Finally, I will address a fundamental result by Rosas-Bazan, which states that a homeomorphism extending through a neighbourhood of the exceptional divisor of the first blow-up implies the topological invariance of the algebraic multiplicity. I will show that the result holds if the homeomorphism extends locally near a singularity, even if it does not extend over the entire divisor.
This is a joint work with Leonardo M. Câmara and Fernando Reis.