English

On finite regular and holomorphic mappings

Algebraic Geometry 2015-03-10 v4

Abstract

Let X,YX, Y be smooth algebraic varieties of the same dimension. Let f,g:XYf, g : X \to Y be finite polynomial mappings. We say that f,gf, g are equivalent if there exists a regular automorphism ΦAut(X)\Phi \in Aut(X) such that f=gΦf = g\circ \Phi. Of course if f,gf, g are equivalent, then they have the same discriminant and the same geometric degree. We show, that conversely there is only a finite number of non-equivalent proper polynomial mappings f:XYf : X \to Y, such that D(f)=VD(f) = V and μ(f)=k.\mu(f) = k. We prove the same statement in the local holomorphic situation. In particular we show that if f:(Cn,0)(Cn,0)f : (\Bbb C^n, 0) \to (\Bbb C^n, 0) is a proper and holomorphic mapping of topological degree two, then there exist biholomorphisms P,Q:(Cn,0)(Cn,0)P,Q : (\Bbb C^n, 0) \to (\Bbb C^n, 0) such that PfQ(x1,x2,...,xn)=(x12,x2,...,xn)P\circ f\circ Q (x_1, x_2,..., x_n) = (x_1^2, x_2, ..., x_n). Moreover, for every proper holomorphic mapping f:(Cn,0)(Cn,0)f : (\Bbb C^n, 0) \to (\Bbb C^n, 0) with smooth discriminant there exist biholomorphisms P,Q:(Cn,0)(Cn,0)P,Q : (\Bbb C^n, 0) \to (\Bbb C^n, 0) such that PfQ(x1,x2,...,xn)=(x1k,x2,...,xn)P\circ f\circ Q (x_1, x_2,..., x_n) = (x_1^k, x_2, ..., x_n), where k=μ(f).k = \mu(f).

Keywords

Cite

@article{arxiv.1404.7466,
  title  = {On finite regular and holomorphic mappings},
  author = {Zbigniew Jelonek},
  journal= {arXiv preprint arXiv:1404.7466},
  year   = {2015}
}
R2 v1 2026-06-22T04:02:11.677Z