English

Dicritical divisors and hypercurvettes

Algebraic Geometry 2025-06-02 v1

Abstract

Germs of rational functions~hh on points pp of smooth varieties~SS define germs of rational maps to the projective line. Assume that pp is in the indeterminacy locus of hh. If π:S^S\pi:\hat{S}\to S is a birational map which is an isomorphism outside pp, then hh lifts to a germ of a rational map on (S^,π1(p))(\hat{S}, \pi^{-1}(p)). The exceptional components EiE_i of π1(p)\pi^{-1}(p) are classified according to the restriction of (the lift of) hh to EiE_i; the dicritical components are those where this restriction induces a dominant map. In a series of papers, Abhyankar and the first named author studied this setting in dimension 22, where the main result is that, for any given π\pi, there is a rational function hh with a prescribed subset of exceptional components that are dicritical of some given degree. The concept of curvette of an exceptional component played a key role in the proof. The second named author extended previously the concept of curvette to the higher dimensional case. Here we use this concept to generalize the above result to arbitrary dimension.

Keywords

Cite

@article{arxiv.2505.24648,
  title  = {Dicritical divisors and hypercurvettes},
  author = {Enrique Artal Bartolo and Willem Veys},
  journal= {arXiv preprint arXiv:2505.24648},
  year   = {2025}
}
R2 v1 2026-07-01T02:50:44.812Z