English

Cusps in $\mathbb{C}^3$ with prescribed ramification

Algebraic Geometry 2023-10-18 v2 Combinatorics Number Theory

Abstract

We study value semigroups associated to germs of maps CC3\mathbb{C} \rightarrow \mathbb{C}^3 with fixed ramification profiles in a distinguished point. We then apply our analysis to deduce that Severi varieties of unicuspidal rational fixed-degree curves with value semigroup S{\rm S} in P3\mathbb{P}^3 are often reducible when S{\rm S} is either 1) the semigroup of a generic cusp whose ramification profile is a supersymmetric triple; or 2) a supersymmetric semigroup with ramification profile given by a supersymmetric triple. In doing so, we uncover new connections with additive combinatorics and number theory.

Keywords

Cite

@article{arxiv.2303.09303,
  title  = {Cusps in $\mathbb{C}^3$ with prescribed ramification},
  author = {Ethan Cotterill and Nathan Kaplan and Renata Vieira Costa},
  journal= {arXiv preprint arXiv:2303.09303},
  year   = {2023}
}

Comments

Adjusted numerical hypotheses to reflect the fact that the degree should be at least the valuation of the conductor of the cusp, which in particular is true whenever $d \geq 2g$

R2 v1 2026-06-28T09:20:08.417Z