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On quartics with the maximal number of the maximal tangency lines

Łukasz Merta, Marcin Zieliński

Abstract

In this note, we examine the arrangements of lines and configurations of points that emerge from Fermat (von Dyck) and Komiya-Kuribayashi quartics. These quartics are characterized by having the maximum number of lines of maximal tangency, that is, lines for which the intersection multiplicity at the tangency point is equal to the degree of the curve. Additionally, we delve into the study of sextactic points on these quartics - points at which there exists a conic with the curve having a local intersection multiplicity of at least 6, which is one more than that observed at a general point - alongside the related configurations of conics.

On quartics with the maximal number of the maximal tangency lines

Abstract

In this note, we examine the arrangements of lines and configurations of points that emerge from Fermat (von Dyck) and Komiya-Kuribayashi quartics. These quartics are characterized by having the maximum number of lines of maximal tangency, that is, lines for which the intersection multiplicity at the tangency point is equal to the degree of the curve. Additionally, we delve into the study of sextactic points on these quartics - points at which there exists a conic with the curve having a local intersection multiplicity of at least 6, which is one more than that observed at a general point - alongside the related configurations of conics.

Paper Structure

This paper contains 6 sections, 13 theorems, 34 equations, 1 figure.

Key Result

Lemma 2.1

The $12$ maximal tangency lines $LF_1, \dots, LF_{12}$ intersect in $48$ double points and $3$ points of multiplicity $4$.

Figures (1)

  • Figure 1: Configuration of $12$ lines passing through the MTPs on the Fermat quartic $x^4 + y^4 + z^4$.

Theorems & Definitions (20)

  • Definition 1.1
  • Definition 1.2
  • Definition 1.3
  • Lemma 2.1
  • proof
  • Proposition 2.2
  • Theorem 2.3
  • proof
  • Proposition 3.1
  • proof
  • ...and 10 more