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arXiv · 1804.06194

Freeness and invariants of rational plane curves

Laurent Busé·Alexandru Dimca·Gabriel Sticlaru
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Abstract

Given a parameterization $\phi$ of a rational plane curve C, we study some invariants of C via $\phi$. We first focus on the characterization of rational cuspidal curves, in particular we establish a relation between the discriminant of the pull-back of a line via $\phi$, the dual curve of C and its singular points. Then, by analyzing the pull-backs of the global differential forms via $\phi$, we prove that the (nearly) freeness of a rational curve can be tested by inspecting the Hilbert function of the kernel of a canonical map. As a by product, we also show that the global Tjurina number of a rational curve can be computed directly from one of its parameterization, without relying on the computation of an equation of C.

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Laurent Busé, Alexandru Dimca, Gabriel Sticlaru. 2018-04-17. Freeness and invariants of rational plane curves. https://doi.org/10.1090/mcom%2F3495

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