19,210 research outputs found
Explicit Solution By Radicals, Gonal Maps and Plane Models of Algebraic Curves of Genus 5 or 6
We give explicit computational algorithms to construct minimal degree (always
) ramified covers of \Prj^1 for algebraic curves of genus 5 and 6.
This completes the work of Schicho and Sevilla (who dealt with the
case) on constructing radical parametrisations of arbitrary genus curves.
Zariski showed that this is impossible for the general curve of genus .
We also construct minimal degree birational plane models and show how the
existence of degree 6 plane models for genus 6 curves is related to the
gonality and geometric type of a certain auxiliary surface.Comment: v3: full version of the pape
On the convex hull of a space curve
The boundary of the convex hull of a compact algebraic curve in real 3-space
defines a real algebraic surface. For general curves, that boundary surface is
reducible, consisting of tritangent planes and a scroll of stationary
bisecants. We express the degree of this surface in terms of the degree, genus
and singularities of the curve. We present algorithms for computing their
defining polynomials, and we exhibit a wide range of examples.Comment: 19 pages, 4 figures, minor change
Rational plane curves parameterizable by conics
We introduce the class of rational plane curves parameterizable by conics as
an extension of the family of curves parameterizable by lines (also known as
monoid curves). We show that they are the image of monoid curves via suitable
quadratic transformations in projective plane. We also describe all the
possible proper parameterizations of them, and a set of minimal generators of
the Rees Algebra associated to these parameterizations, extending well-known
results for curves parameterizable by lines.Comment: 28 pages, 1 figure. Revised version. Accepted for publication in
Journal of Algebr
Point counting on curves using a gonality preserving lift
We study the problem of lifting curves from finite fields to number fields in
a genus and gonality preserving way. More precisely, we sketch how this can be
done efficiently for curves of gonality at most four, with an in-depth
treatment of curves of genus at most five over finite fields of odd
characteristic, including an implementation in Magma. We then use such a lift
as input to an algorithm due to the second author for computing zeta functions
of curves over finite fields using -adic cohomology
The 2-Hessian and sextactic points on plane algebraic curves
In an article from 1865, Arthur Cayley claims that given a plane algebraic
curve there exists an associated 2-Hessian curve that intersects it in its
sextactic points. In this paper we fix an error in Cayley's calculations and
provide the correct defining polynomial for the 2-Hessian. In addition, we
present a formula for the number of sextactic points on cuspidal curves and tie
this formula to the 2-Hessian. Lastly, we consider the special case of rational
curves, where the sextactic points appear as zeros of the Wronski determinant
of the 2nd Veronese embedding of the curve.Comment: Updated version to be published in Mathematica Scandinavica.
Substantially rewritten, but with essential results unchanged. Contains
results from first author's master's thesis. 21 pages, 2 figure
First Steps Towards Radical Parametrization of Algebraic Surfaces
We introduce the notion of radical parametrization of a surface, and we
provide algorithms to compute such type of parametrizations for families of
surfaces, like: Fermat surfaces, surfaces with a high multiplicity (at least
the degree minus 4) singularity, all irreducible surfaces of degree at most 5,
all irreducible singular surfaces of degree 6, and surfaces containing a pencil
of low-genus curves. In addition, we prove that radical parametrizations are
preserved under certain type of geometric constructions that include offset and
conchoids.Comment: 31 pages, 7 color figures. v2: added another case of genus
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