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We show that a real rational (over $\C$) surfaces are quasi-simple, i.e., that such a surface is determined up to deformation in the class of real surfaces by the topological type of its real structure.

Algebraic Geometry · Mathematics 2008-03-21 Alex Degtyarev , Viatcheslav Kharlamov

We prove that the complex surfaces parametrizing cuboids and face cuboids, as well as their minimal resolution of singularities, have trivial fundamental group. We then compute the fundamental group of certain open smooth subvarieties of…

Algebraic Geometry · Mathematics 2024-09-18 David Jarossay , Francesco Maria Saettone , Yotam Svoray

Given a unirational parameterization of a surface, we present a general algorithm to determine a birational parameterization without using parameterization algorithms. Additionally, if the surface is assumed to have a birational…

Algebraic Geometry · Mathematics 2022-11-15 Jorge Caravantes , Sonia Pérez-Díaz , J. Rafael Sendra

Toute hypersurface cubique lisse complexe de dimension au moins 2 dont l'\'equation est donn\'ee par l'annulation d'une somme de formes cubiques \`a variables s\'epar\'ees, chaque forme impliquant au plus trois variables, est…

Algebraic Geometry · Mathematics 2017-01-10 Jean-Louis Colliot-Thélène

We classify real families of minimal degree rational curves that cover an embedded rational surface. A corollary is that if the projective closure of a smooth surface is not biregular isomorphic to the projective closure of the unit-sphere,…

Algebraic Geometry · Mathematics 2021-03-09 Niels Lubbes

We prove that the Brauer group of the generic diagonal surface of arbitrary degree is trivial. The same method is applied to surfaces whose equation can be written as the sum of two bilinear forms. This uses a general criterion for the…

Algebraic Geometry · Mathematics 2025-09-12 Damián Gvirtz-Chen , Alexei Skorobogatov

We present a method for computing all the symmetries of a rational ruled surface defined by a rational parametrization which works directly in parametric rational form, i.e. without computing or making use of the implicit equation of the…

Algebraic Geometry · Mathematics 2018-06-27 Alcázar Arribas , Juan Gerardo , Emily Quintero

We define the notion of generalized logarithmic sheaves on a smooth projective surface, associated to a pair consisting of a reduced curve and some fixed points on it. We then set up the study of the Torelli property in this setting,…

Algebraic Geometry · Mathematics 2023-02-16 Sukmoon Huh , Simone Marchesi , Joan Pons-Llopis , Jean Vallès

We give necessary and sufficient topological conditions for a simple closed curve on a real rational surface to be approximable by smooth rational curves. We also study approximation by smooth rational curves with given complex…

Algebraic Geometry · Mathematics 2025-05-26 János Kollár , Frédéric Mangolte

By the famous ADE classification rational double points are simple. Rational triple points are also simple. We conjecture that the simple normal surface singularities are exactly those rational singularities, whose resolution graph can be…

Algebraic Geometry · Mathematics 2013-03-05 Jan Stevens

In characteristic $p>0$ and for $q$ a power of $p$, we compute the number of nonplanar rational curves of arbitrary degrees on a smooth Hermitian surface of degree $q+1$ under the assumption that the curves have a parametrization given by…

Algebraic Geometry · Mathematics 2020-03-31 Norifumi Ojiro

For a smooth plane cubic $B$, we count curves $C$ of degree $d$ such that the normalizations of $C\backslash B$ are isomorphic to $\Bbb A^1$, for $d\leq7$ (for $d=7$ under some assumption). We also count plane rational quartic curves…

alg-geom · Mathematics 2008-02-03 Nobuyoshi Takahashi

This paper proposes a simple technique of curve and surface construction with B-splines. Given a control polygon or a control mesh together with node ordinates corresponding to all control points, a rational curve or surface is obtained by…

Numerical Analysis · Mathematics 2025-12-02 Xunnian Yang

A parameterized surface can be represented as a projection from a certain toric surface. This generalizes the classical homogeneous and bihomogeneous parameterizations. We extend to the toric case two methods for computing the implicit…

Algebraic Geometry · Mathematics 2007-05-23 Amit Khetan , Carlos D'Andrea

We show that the roots of any smooth curve of polynomials with only real roots can be parametrized twice differentiably (but not better).

Classical Analysis and ODEs · Mathematics 2007-05-23 Andreas Kriegl , Mark Losik , Peter W. Michor

We classify all complex surfaces with quotient singularities that do not contain any smooth rational curves, under the assumption that the canonical divisor of the surface is not pseudo-effective. As a corollary we show that if $X$ is a log…

Algebraic Geometry · Mathematics 2018-10-17 Ziquan Zhuang

We compute the rational cohomology of the universal family of smooth cubic surfaces using Vassiliev's method of simplicial resolution. Modulo embedding, the universal family has cohomology isomorphic to that of $\mathbb{P}^2$. A consequence…

Algebraic Geometry · Mathematics 2019-02-19 Ronno Das

Let $\mathcal{L}$ be a line bundle on a smooth and proper scheme $X$ over $S$. We compute, in the case where $S$ is smooth over a field of characteristic $0$, the virtual fundamental class of the closed subset of $S$ consisting of those…

Algebraic Geometry · Mathematics 2026-02-12 Amira Tlemsani

It is still a challenging task of today to recognize the type of a given algebraic surface which is described only by its implicit representation. In~this paper we will investigate in more detail the case of canal surfaces that are often…

Symbolic Computation · Computer Science 2014-10-15 Jan Vršek , Miroslav Lávička

We classify special self-birational transformations of the smooth quadric threefold and fourfold, $Q^3$ and $Q^4$. It turns out that there is only one such example in each dimension. In the case of $Q^3$, it is given by the linear system of…

Algebraic Geometry · Mathematics 2024-07-17 Jordi Hernández
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