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A closed algebraic embedding of $\mathbb{C}^*=\mathbb{C}^1\setminus\{0\}$ into $\mathbb{C}^2$ is 'sporadic' if for every curve $A\subseteq \mathbb{C}^2$ isomorphic to an affine line the intersection with $\mathbb{C}^*$ is at least $2$.…

Algebraic Geometry · Mathematics 2019-04-30 Mariusz Koras , Karol Palka , Peter Russell

We enumerate the singular algebraic curves in a complete linear system on a smooth projective surface. The system must be suitably ample in a rather precise sense. The curves may have up to eight nodes, or a triple point of a given type and…

Algebraic Geometry · Mathematics 2007-05-23 Steven Kleiman , Ragni Piene

We present an effective criterion to determine if a normal analytic compactification of C^2 with one irreducible curve at infinity is algebraic or not. As a by product we establish a correspondence between normal algebraic compactifications…

Algebraic Geometry · Mathematics 2016-10-19 Pinaki Mondal

We give a novel and effective criterion for algebraicity of rational normal analytic surfaces constructed from resolving the singularity of an irreducible curve-germ on $CP^2$ and contracting the strict transform of a given line and all but…

Algebraic Geometry · Mathematics 2012-11-20 Pinaki Mondal

We classify 'primitive normal compactifications' of C^2 (i.e. normal analytic surfaces containing C^2 for which the curve at infinity is irreducible), compute the moduli space of these surfaces and their groups of auomorphisms. In…

Algebraic Geometry · Mathematics 2016-09-20 Pinaki Mondal

We consider flat families of reduced curves on a smooth surface S such that each member C has the same number of singularities of fixed singularity types and the corresponding (locally closed) subscheme H of the Hilbert scheme of S. We are…

alg-geom · Mathematics 2008-02-03 Gert-Martin Greuel , Christoph Lossen

In this paper we prove that the unit ball $\mathbb{B}$ of $\mathbb{C}^2$ admits complete properly embedded complex curves of any given topological type. Moreover, we provide examples containing any given closed discrete subset of…

Complex Variables · Mathematics 2018-03-16 Antonio Alarcon , Josip Globevnik

We complete the classification of the smooth, closed, oriented 4-manifolds having Euler characteristic less than four and a horizontal handlebody decomposition of genus one. We use the classification result to find a large family of…

Geometric Topology · Mathematics 2025-08-20 Paolo Lisca , Andrea Parma

We provide several families of compact complex curves embedded in smooth complex surfaces such that no neighborhood of the curve can be embedded in an algebraic surface. Different constructions are proposed, by patching neighborhoods of…

Algebraic Geometry · Mathematics 2024-07-30 Maycol Falla Luza , Frank Loray , Paulo Sad

We study curve singularities in a smooth surface relative to a smooth boundary curve. We consider the semiuniversal deformations and equisingular deformations of curves with a fixed local intersection number $w$ with the boundary, and prove…

Algebraic Geometry · Mathematics 2025-10-20 Nobuyoshi Takahashi

Given a smooth complex variety $X$, an algebraically skew embedding of $X$ is an embedding of $X$ into a complex projective space $\mathbb{P}^N$ such that for any two points $x,y\in X$, their embedded tangent spaces in $\mathbb{P}^N$ do not…

Algebraic Geometry · Mathematics 2025-05-06 Andy B. Day

In $\mathbb{S}^2 \times \mathbb{R}$ there is a two-parameter family of properly embedded minimal annuli foliated by circles. In this paper we show that this family contains all properly embedded minimal annuli. We use the description of…

Differential Geometry · Mathematics 2020-12-21 L. Hauswirth , M. Kilian , M. U. Schmidt

We identify a class of smooth Banach *-algebras that are differential subalgebras of commutative C*-algebras whose openness of multiplication is completely determined by the topological stable rank of the target C*-algebra. We then show…

Operator Algebras · Mathematics 2024-11-27 Tomasz Kania , Natalia Maślany

A non-singular connected algebraic curve $A$ in a simply connected algebraic surface $X$ can be knotted so that its homology class and the fundamental group of its complement in $X$ is preserved, provided $A$ is sufficiently complex (not…

Geometric Topology · Mathematics 2007-05-23 Sergey Finashin

We find new examples of complex surfaces with countably many non-isomorphic algebraic structures. Here is one such example: take an elliptic curve $E$ in $\mathbb P^2$ and blow up nine general points on $E$. Then the complement $M$ of the…

Complex Variables · Mathematics 2023-03-21 Anna Abasheva , Rodion Déev

In order to study projections of smooth curves, we introduce multifiltrations obtained by combining flags of osculating spaces. We classify all configurations of singularities occurring for a projection of a smooth curve embedded by a…

Algebraic Geometry · Mathematics 2020-01-14 Jarosław Buczyński , Nathan Ilten , Emanuele Ventura

The main result of the paper states that a connected complex affine algebraic curve is Lipschitz normally embedded (shortened to LNE afterwards) in $\mathbb{C}^n$ if and only if its germ at any singular point is a finite union of…

Algebraic Geometry · Mathematics 2023-11-28 André Costa , Vincent Grandjean , Maria Michalska

We study families of rational curves on an algebraic variety satisfying incidence conditions. We prove an analogue of bend-and-break: that is, we show that under suitable conditions, such a family must contain reducibles. In the case of…

Algebraic Geometry · Mathematics 2020-06-26 Ziv Ran

In the long paper "Family Blowup formula, Admissible Graphs and the Enumeration of Singular Curves (I)" (appearing in JDG), the author solved the enumeration problem of nodal (or general singular) curve counting on algebraic surfaces by…

Algebraic Geometry · Mathematics 2007-05-23 Ai-Ko Liu

We prove that any separable exact C*-algebra is isomorphic to a subalgebra of the Cuntz algebra ${\cal O}_2.$ We further prove that if $A$ is a simple separable unital nuclear C*-algebra, then ${\cal O}_2 \otimes A \cong {\cal O}_2,$ and…

funct-an · Mathematics 2016-08-15 Eberhard Kirchberg , N. Christopher Phillips
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