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This is an expanded version of our work [AN88], 1988, in Russian. We classify del Pezzo surfaces over C with log terminal singularities of index \le 2. By classification, we understand a description of the intersection graph of all…

Algebraic Geometry · Mathematics 2007-05-23 Valery Alexeev , Viacheslav V. Nikulin

We study the problem of existence of stationary disks for domains in almost complex manifolds. As a consequence of our results, we prove that any almost complex domains which is a small deformations of a strictly linearly convex domain $D…

Complex Variables · Mathematics 2009-05-13 Giorgio Patrizio , Andrea Spiro

We state a number of conjectures that together allow one to classify a broad class of del Pezzo surfaces with cyclic quotient singularities using mirror symmetry. We prove our conjectures in the simplest cases. The conjectures relate…

We prove unobstructed deformations for compact Kaehlerian even-dimensional Poisson manifolds whose Poisson tensor degenerates along a divisor with mild singularities. Examples include Hilbert schemes of del Pezzo surfaces.

Algebraic Geometry · Mathematics 2016-09-21 Ziv Ran

We introduce the $2$-nodal spherical deformation of certain singular fibers of genus $2$ fibrations, and use such deformations to construct various examples of simply connected minimal symplectic $4$-manifolds with small topology. More…

Geometric Topology · Mathematics 2021-02-17 Anar Akhmedov , Sümeyra Sakalli

In this paper, we classify codimension one foliations on adjoint varieties with most positive anti-canonical class. We show that on adjoint varieties with Picard number one, these foliations are always induced by a pencil of hyperplane…

Algebraic Geometry · Mathematics 2025-07-31 Crislaine Kuster

This paper, which is an outgrowth of a previous paper of the authors, continues the study of dimension 1 foliations on non-metrisable manifolds emphasising some anomalous behaviours. We exhibit surfaces with various extra properties like…

General Topology · Mathematics 2013-03-28 Mathieu Baillif , Alexandre Gabard , David Gauld

In this paper we give a criterion for birational rigidity of del Pezzo fibrations of degree 1 and 2 with only quotient singularities. As an application, we prove birational rigidity of suitable del Pezzo fibrations admitting an action of…

Algebraic Geometry · Mathematics 2015-04-07 Takuzo Okada

Let $X$, $Y$ be Fano threefolds of Picard number one and such that the ample generators of Picard groups are very ample. Let $X$ be of index one and $Y$ be of index two. It is shown that the only morphisms from $X$ to $Y$ are double…

Algebraic Geometry · Mathematics 2007-05-23 Ekaterina Amerik

Generalising toric geometry we study compact varieties admitting lower dimensional torus actions. In particular we describe divisors on them in terms of convex geometry and give a criterion for their ampleness. These results may be used to…

Algebraic Geometry · Mathematics 2010-12-16 Hendrik Süß

We describe the structure of regular codimension $1$ foliations with numerically projectively flat tangent bundle on complex projective manifolds of dimension at least $4$. Along the way, we prove that either the normal bundle of a regular…

Algebraic Geometry · Mathematics 2024-01-09 Stéphane Druel

We study the space of deformations of a smooth foliation of the 5-sphere by complex manifolds

Differential Geometry · Mathematics 2011-11-10 Laurent Meersseman , Alberto Verjovsky

Let $X$ be a complex smooth Fano variety of dimension at least four. In this paper, we classify such $X$ when the pseudoindex is at least $n-2$ and the Picard number greater than one. We also discuss the relations between pseudoindex and…

Algebraic Geometry · Mathematics 2024-07-12 Kiwamu Watanabe

Let $X$ be an $n$-dimensional complex Fano manifolds $(n\geq 3)$. Assume that $X$ contains a divisor $A$, which is isomorphic to a rational homogeneous space with Picard number one, such that the conormal bundle $\mathscr{N}^*_{A/X}$ is…

Algebraic Geometry · Mathematics 2021-07-30 Jie Liu

In this article, we describe the structure of codimension one foliations with canonical singularities and numerically trivial canonical class on varieties with terminal singularities, extending a result of Loray, Pereira and Touzet to this…

Algebraic Geometry · Mathematics 2023-02-22 Stéphane Druel

Extending some results of Crauder and Katz, and Ein and Shepherd-Barron on special Cremona transformations, we study birational transformations of the complex projective spaces onto prime Fano manifolds such that the base locus X of the…

Algebraic Geometry · Mathematics 2013-09-13 Alberto Alzati , José Carlos Sierra

We present a few general results on foliations of 4-manifolds by surfaces: existence, tautness, relations to minimal genus of embedded surfaces; as well as some open problems. We hope to stimulate interest in this area.

Geometric Topology · Mathematics 2007-05-23 Alexandru Scorpan

We show that deformations of a surjective morphism onto a Fano manifold of Picard number 1 are unobstructed and rigid modulo the automorphisms of the target, if the variety of minimal rational tangents of the Fano manifold is non-linear or…

Algebraic Geometry · Mathematics 2009-08-17 Jun-Muk Hwang

We prove Manin's conjecture for a split singular quartic del Pezzo surface with singularity type $2\Aone$ and eight lines. This is achieved by equipping the surface with a conic bundle structure. To handle the sum over the family of conics,…

Number Theory · Mathematics 2014-02-26 Daniel Loughran

We study the invariant theory of singular foliations of the projective plane. Our first main result is that a foliation of degree m>1 is not stable only if it has singularities in dimension 1 or contains an isolated singular point with…

Algebraic Geometry · Mathematics 2011-01-27 Eduardo Esteves , Marina Marchisio