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We investigate, using purely combinatorial methods, structural and algorithmic properties of linear equivalence classes of divisors on tropical curves. In particular, an elementary proof of the Riemann-Roch theorem for tropical curves,…

Combinatorics · Mathematics 2017-07-31 Jan Hladký , Daniel Král' , Serguei Norine

For every $n\geq 3$, we exhibit infinitely many extremal effective divisors on the moduli space of genus one curves with $n$ marked points.

Algebraic Geometry · Mathematics 2013-04-02 Dawei Chen , Izzet Coskun

L. Szpiro and T. Tucker recently proved that under mild conditions, the valuation of the minimal discriminant of an elliptic curve with semistable reduction over a discrete valuation ring can be expressed in terms of intersections between…

Number Theory · Mathematics 2012-07-24 Robin de Jong

A smooth real curve is called separating in case the complement of the real locus inside the complex locus is disconnected. This is the case if there exists a morphism to the projective line whose inverse image of the real locus of the…

Algebraic Geometry · Mathematics 2011-09-13 Marc Coppens

In the theory of algebraic function fields and their applications to the information theory, the Riemann-Roch theorem plays a fundamental role. But its use, delicate in general, is efficient and practical for applications especially in the…

Algebraic Geometry · Mathematics 2026-02-17 S Ballet , M Koutchoukali

We compute generators and relations for the section ring of a rational divisor on an elliptic curve. Our technique generalizes the work of O'Dorney (in genus zero) and Voight--Zureick-Brown (for specific divisors arising from the study of…

Number Theory · Mathematics 2024-03-05 Michael Cerchia , Jesse Franklin , Evan O'Dorney

The restrictions on the topology of nonsingular plane projective real algebraic curves of odd degree, obtained by O. Viro and the author in the paper published in the early 90s, are extended to flexible curves lying on an almost complex…

Algebraic Geometry · Mathematics 2022-03-29 V. I. Zvonilov

The Jacobian $J$ of a complete, smooth, connected curve $X$ admits a canonical divisor $\Theta$, called the Theta divisor. It is well-known that $\Theta$ is ample and, in fact, $3\Theta$ is very ample. For a general complete, integral curve…

alg-geom · Mathematics 2008-02-03 Eduardo Esteves

Motivated by the classical Theorems of Picard and Siegel and their generalizations, we define the notion of an {\it essentially large} effective divisor and derive some of its geometric and arithmetic consequences. We then prove that on a…

Algebraic Geometry · Mathematics 2010-06-08 Gordon Heier , Min Ru

Given a graded sequence of ideals (a_m) on a smooth variety $X$ having finite log canonical threshold, suppose that for every m we have a divisor E_m over X that computes the log canonical threshold of a_m, and such that the log…

Algebraic Geometry · Mathematics 2011-07-05 Mattias Jonsson , Mircea Mustata

In this article we prove a finiteness result on the number of log minimal models for $3$-folds in char $p>5$. We then use this result to prove a version of Batyrev's conjecture on the structure of nef cone of curves on $3$-folds in…

Algebraic Geometry · Mathematics 2018-09-17 Omprokash Das

Let U be a smooth quasi-projective variety over a field k that is finite, the algebraic closure of a finite field or algebraically closed of characteristic 0. Let X be a suitable projective compactification of U, and D an effective divisor…

Algebraic Geometry · Mathematics 2023-11-08 Henrik Russell

Inside the symmetric product of a very general curve, we consider the codimension-one subvarieties of symmetric tuples of points imposing exceptional secant conditions on linear series on the curve of fixed degree and dimension. We compute…

Algebraic Geometry · Mathematics 2016-02-03 Nicola Tarasca

It goes back to Ahlfors that a real algebraic curve $C$ admits a separating morphism $f$ to the complex projective line if and only if the real part of the curve disconnects its complex part, i.e. the curve is \textit{separating}. The…

Algebraic Geometry · Mathematics 2023-10-31 Matilde Manzaroli

There is a close relationship between the embedded topology of complex plane curves and the (group-theoretic) arithmetic of elliptic curves. In a recent paper, we studied the topology of some arrangements of curves which include a special…

Algebraic Geometry · Mathematics 2020-12-10 E. Artal Bartolo , S. Bannai , T. Shirane , H. Tokunaga

Suppose $X$ is a smooth projective connected curve defined over an algebraically closed field of characteristic $p>0$ and $B \subset X$ is a finite, possibly empty, set of points. Booher and Cais determined a lower bound for the $a$-number…

We introduce and begin the topological study of real rational plane curves, all of whose inflection points are real. The existence of such curves is a corollary of results in the real Schubert calculus, and their study has consequences for…

Algebraic Geometry · Mathematics 2010-03-29 Viatcheslav Kharlamov , Frank Sottile

In the paper \cite{Lau16}, it was shown that the restriction of a pseudoeffective divisor $D$ to a subvariety $Y$ with nef normal bundle is pseudoeffective. Assuming the normal bundle is ample and that $D|_Y$ is not big, we prove that the…

Algebraic Geometry · Mathematics 2019-07-10 Chung-Ching Lau

We compute divisors class groups of singular surfaces. Most notably we produce an exact sequence that relates the Cartier divisors and almost Cartier divisors of a surface to the those of its normalization. This generalizes Hartshorne's…

Commutative Algebra · Mathematics 2013-01-16 Robin Hartshorne , Claudia Polini

We propose a linear version of the weighted bounded negativity conjecture. It considers a smooth projective surface $X$ over an algebraically closed field of characteristic zero and predicts the existence of a common lower bound on…

Algebraic Geometry · Mathematics 2025-01-27 Carlos Galindo , Francisco Monserrat , Elvira Pérez-Callejo