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In this paper, we prove that: For any given finitely many distinct points $P_1,...,P_r$ and a closed subvariety $S$ of codimension $\geq 2$ in a complete toric variety over a uncountable (characteristic 0) algebraically closed field, there…

Algebraic Geometry · Mathematics 2009-05-12 Yifei Chen , Vyacheslav Shokurov

We study embedded rational curves in projective toric varieties. Generalizing results of the first author and Zotine for the case of lines, we show that any degree $d$ rational curve in a toric variety $X$ can be constructed from a special…

Algebraic Geometry · Mathematics 2026-01-14 Nathan Ilten , Jake Levinson

Polarized and $G$-polarized CR manifolds are smooth manifolds endowed with a double structure: a real foliation $\Cal F$ (given by the action of a Lie group $G$ in the $G$-polarized case) and a transverse CR distribution $(E,J)$. Polarized…

Complex Variables · Mathematics 2014-01-27 Laurent Meersseman

A classification theorem is given of smooth threefolds of $\Bbb P^5$ covered by a family of dimension at least three of plane integral curves of degree $d\geq 2.$ It is shown that for such a threefold $X$ there are two possibilities:…

alg-geom · Mathematics 2008-02-03 Emilia Mezzetti , Dario Portelli

We consider rationally connected complex projective manifolds M and show that their loop spaces--infinite dimensional complex manifolds--have properties similar to those of M. Furthermore, we give a finite dimensional application concerning…

Algebraic Geometry · Mathematics 2007-05-23 L. Lempert , E. Szabo

We establish a conjecture of Mumford characterizing rationally connected complex projective manifolds in several cases.

Algebraic Geometry · Mathematics 2017-05-05 Vladimir Lazić , Thomas Peternell

We prove that, over a smooth quasi-projective curve, the set of non-isotrivial, smooth and projective families of polarized varieties with a fixed Hilbert polynomial and semi-ample canonical bundle is bounded. This extends the boundedness…

Algebraic Geometry · Mathematics 2026-05-26 Kenneth Ascher , Behrouz Taji

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

In this paper we prove that a smooth family of canonically polarized manifolds parametrized by a special (in the sense of Campana) quasi-projective variety is isotrivial.

Algebraic Geometry · Mathematics 2019-02-20 Behrouz Taji

The paper is a generalization of a result of I. Dolgachev, M. Mendes Lopes, and R. Pardini. We prove that a smooth projective complex surface $X$, not necessarily minimal, contains $h^{1,1}(X)-1$ disjoint $(-2)$-curves if and only if $X$ is…

Algebraic Geometry · Mathematics 2009-12-29 JongHae Keum

Let F be a polarized irreducible holomorphic symplectic fourfold, deformation equivalent to the Hilbert scheme parametrizing length-two zero-dimensional subschemes of a K3 surface. The homology group H^2(F,Z) is equipped with an integral…

Algebraic Geometry · Mathematics 2010-03-05 Brendan Hassett , Yuri Tschinkel

Under natural hypotheses we give an upper bound on the dimension of families of singular curves with hyperelliptic normalizations on a surface S with p_g(S) >0 via the study of the associated families of rational curves in Hilb^2(S). We use…

Algebraic Geometry · Mathematics 2007-05-25 Flaminio Flamini , Andreas Leopold Knutsen , Gianluca Pacienza , Edoardo Sernesi

Let $(X,D)$ be a smooth log pair over $\mathbb{C}$ such that the complement $U := X \setminus D$ carries a maximally varied family of polarized manifolds. We prove a version of second main theorem on $(X,D)$ by using the Viehweg-Zuo…

Algebraic Geometry · Mathematics 2020-08-05 Ruiran Sun

As a result of our study of the hyperbolicity of the moduli space of polarized manifold, we give a general big Picard theorem for a holomorphic curve on a log-smooth pair $(X,D)$ such that $W=X\setminus D$ admits a Finsler pseudometric that…

Algebraic Geometry · Mathematics 2021-07-20 Ya Deng , Steven Lu , Ruiran Sun , Kang Zuo

We show the existence of metrically dense entire curves in rationally connected complex projective manifolds confirming for this case a conjecture according to which such entire curves on projective manifolds exist if and only if these are…

Algebraic Geometry · Mathematics 2020-01-09 Frederic Campana , Joerg Winkelmann

We obtain new examples and the complete list of the rational cuspidal plane curves $C$ with at least three cusps, one of which has multiplicity ${\rm deg}\,C - 2$. It occurs that these curves are projectively rigid. We also discuss the…

alg-geom · Mathematics 2008-02-03 H. Flenner , M. Zaidenberg

We prove that for any rationally connected threefold $X$, there exists a smooth projective surface $S$ and a family of $1$-cycles on $X$ parameterized by $S$, inducing an Abel-Jacobi isomorphism ${\rm Alb}(S)\cong J^3(X)$. This statement…

Algebraic Geometry · Mathematics 2023-04-14 Claire Voisin

Let X be a complex, rationally connected, projective manifold. We show that X admits a modification X' that contains a quasi-line, ie a smooth rational curve whose normal bundle is a direct sum of copies of O_{P^1}(1). For manifolds…

Algebraic Geometry · Mathematics 2007-05-23 Paltin Ionescu , Daniel Naie

We determine the rational divisor class group of the moduli spaces of smooth pointed hyperelliptic curves and of their Deligne-Mumford compactification, over the field of complex numbers.

Algebraic Geometry · Mathematics 2020-02-18 Federico Scavia

Complex contact manifolds have recently received considerable attention. Many of the newer publications approach contact manifolds via the covering family of minimal rational curves. This short note furthers the study of these curves. It is…

Algebraic Geometry · Mathematics 2007-05-23 Stefan Kebekus