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We classify quartic del Pezzo surface fibrations over the projective line via numerical invariants, giving explicit examples for small values of the invariants. For generic such fibrations, we describe explicitly the geometry of spaces of…

Algebraic Geometry · Mathematics 2013-01-31 Brendan Hassett , Yuri Tschinkel

We obtain bounds on the least dimension of an affine space that can contain an $n$-dimensional submanifold without any pairs of parallel or intersecting tangent lines at distinct points. This problem is closely related to the generalized…

Differential Geometry · Mathematics 2007-05-23 M. Ghomi , S. Tabachnikov

Let k be an algebraically closed field of characteristic 0. A del Pezzo threefold F with maximal Picard number is isomorphic to P^1xP^1xP^1, where P^1 is the projective line over k. In the present paper we completely classify locally free…

Algebraic Geometry · Mathematics 2014-12-10 Gianfranco Casnati , Daniele Faenzi , Francesco Malaspina

In this note, we give a brief exposition on the differences and similarities between strictly nef and ample vector bundles, with particular focus on the circle of problems surrounding the geometry of projective manifolds with strictly nef…

Algebraic Geometry · Mathematics 2020-09-03 Jie Liu , Wenhao Ou , Xiaokui Yang

Let $X$ be a complex manifold and $L$ be a holomorphic line bundle on $X$. Assume that $L$ is semi-positive, namely $L$ admits a smooth Hermitian metric with semi-positive Chern curvature. Let $Y$ be a compact K\"ahler submanifold of $X$…

Complex Variables · Mathematics 2020-03-09 Takayuki Koike

We show that the fundamental groups of any two closed irreducible non-geometric graph-manifolds are quasi-isometric. This answers a question of Kapovich and Leeb. We also classify the quasi-isometry types of fundamental groups of…

Geometric Topology · Mathematics 2010-04-13 Jason A. Behrstock , Walter D. Neumann

In this article, we study convex affine domains which can cover a compact affine manifold. For this purpose, we first show that every strictly convex quasi-homogeneous projective domain has at least $C^1$ boundary and it is an ellipsoid if…

Geometric Topology · Mathematics 2007-05-23 Kyeonghee Jo

We study global deformations of certain projective bundles over projective spaces. We show that any projective global deformation of a projective bundle over $\bP^1$ carries the structure of a projective bundle over some projective space.…

Algebraic Geometry · Mathematics 2016-07-27 Florian Schrack

We characterize $q$-ample Ulrich bundles on a variety $X \subseteq \mathbb P^N$ with respect to $(q+1)$-dimensional linear spaces contained in $X$.

Algebraic Geometry · Mathematics 2024-03-29 Angelo Felice Lopez , Debaditya Raychaudhury

Some classification results for ample vector bundles of rank 2 on Hirzebruch surfaces, and on Del Pezzo surfaces, are obtained. In particular, we classify rank-2 ample vector bundles with $c_2$ less than 7 on Hirzebruch surfaces, and with…

alg-geom · Mathematics 2008-02-03 Hironobu Ishihara

We study the Kodaira dimension of a real parallelizable manifold $M$, with an almost complex structure $J$ in standard form with respect to a given parallelism. For $X = (M, J)$ we give conditions under which $\operatorname{kod}(X) = 0$. We…

Differential Geometry · Mathematics 2023-07-26 Andrea Cattaneo , Antonella Nannicini , Adriano Tomassini

We classify closed, conformally flat Lorentzian manifolds of dimension $n \geq 3$ with unipotent holonomy in PO(2,n). They are all Kleinian and fall into four different geometric types according to the intersection of the image of the…

Differential Geometry · Mathematics 2024-05-15 Rachel Lee , Karin Melnick

Given a complex projective surface with an ADE singularity and p_{g}=0, we construct ADE bundles over it and its minimal resolution. Furthermore, we descibe their minuscule representation bundles in terms of configurations of (reducible)…

Algebraic Geometry · Mathematics 2013-01-04 Yunxia Chen , Naichung Conan Leung

We complete the classification of automorphism groups of del Pezzo surfaces over algebraically closed fields of odd positive characteristic.

Algebraic Geometry · Mathematics 2023-05-19 Igor Dolgachev , Gebhard Martin

We classify, up to homeomorphism, all closed manifolds having the homotopy type of a connected sum of two copies of real projective n-space.

Geometric Topology · Mathematics 2016-05-18 Jeremy Brookman , James F. Davis , Qayum Khan

We classify del Pezzo non-commutative surfaces that are finite over their centres and have no worse than canonical singularities. Using the minimal model program, we introduce the minimal model of such surfaces. We first classify the…

Algebraic Geometry · Mathematics 2020-02-13 Amir Nasr

We construct first examples of singular del Pezzo surfaces with Zariski dense exceptional sets in Manin's conjecture, varying in degrees $1, 2$ and $3$. The obstructions arise from accumulating quasi-\'etale covers. We classify all…

Algebraic Geometry · Mathematics 2025-03-05 Runxuan Gao

We find a characterization for Fano 4-folds $X$ with Lefschetz defect $\delta_{X}=3$: besides the product of two del Pezzo surfaces, they correspond to varieties admitting a conic bundle structure $f\colon X\to Y$ with…

Algebraic Geometry · Mathematics 2019-06-26 Pedro Montero , Eleonora Anna Romano

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 give a characterization of all del Pezzo surfaces of degree 6 over an arbitrary field $F$. A surface is determined by a pair of separable algebras. These algebras are used to compute the Quillen $K$-theory of the surface. As a…

Algebraic Geometry · Mathematics 2008-05-02 Mark Blunk