EuDML | Browse

Una contrazione su una varietà proiettiva liscia $X$ è data da una mappa $φ : X \to Z$ propria, suriettiva e a fibre connesse in una varietà irriducibile normale $Z$ . La contrazione si dice di Fano-Mori se inoltre $- K_{X}$ è $φ$ -ampio. Nel lavoro, naturale seguito e completamento delle ricerche introdotte in [A-W3], si studiano diversi aspetti delle contrazioni di Fano-Mori attraverso esempi (capitolo 1) e teoremi di struttura (capitoli 3 e 4). Si discutono anche alcune applicazioni allo studio di morfismi birazionali propri...

Cyclic coverings of Fano threefolds

Sławomir Cynk (2003)

Annales Polonici Mathematici

We describe a series of Calabi-Yau manifolds which are cyclic coverings of a Fano 3-fold branched along a smooth divisor. For all the examples we compute the Euler characteristic and the Hodge numbers. All examples have small Picard number $ϱ = h^{1, 1}$ .

Defect series and nonrational Hilbert modular threefolds.

H.G. Grundmann (1994)

Mathematische Annalen

Defects of Cusp Singularities.

Emery Thomas (1983)

Mathematische Annalen

Defects of cusp singularities and the classification of Hilbert modular threefolds.

H.G. Grundmann (1992)

Mathematische Annalen

Divisor class groups of some 3-dimensional singularities

Y. Alwadi, B. Dgheim, M. Roczen (1990)

Banach Center Publications

Double covers and Calabi-Yau varieties

Sławomir Cynk, Tomasz Szemberg (1998)

Banach Center Publications

Elementary Contractions of Gorenstein Threefolds.

Steven Cutkosky (1988)

Mathematische Annalen

Elliptic curves and rank-2 vector bundles on the prime Fano threefold of genus 7.

Iliev, Atanas, Markushevich, Dimitri (2004)

Advances in Geometry

Equivalence of families of singular schemes on threefolds and on ruled fourfolds.

Flaminio Flamini (2004)

Collectanea Mathematica

The main purpose of this paper is twofold. We first analyze in detail the meaningful geometric aspect of the method introduced in [12], concerning families of irreducible, nodal curves on a smooth, projective threefold X. This analysis gives some geometric interpretations not investigated in [12] and highlights several interesting connections with families of other singular geometric objects related to X and to other varieties. Then we use this method to study analogous problems for families of...

Estimates of the number of rational mappings from a fixed variety to varieties of general type

Tanya Bandman, Gerd Dethloff (1997)

Annales de l'institut Fourier

First we find effective bounds for the number of dominant rational maps $f : X \to Y$ between two fixed smooth projective varieties with ample canonical bundles. The bounds are of the type ${A \cdot K_{X}^{n}}^{{B \cdot K_{X}^{n}}^{2}}$ , where $n = \dim X$ , $K_{X}$ is the canonical bundle of $X$ and $A, B$ are some constants, depending only on $n$ .Then we show that for any variety $X$ there exist numbers $c (X)$ and $C (X)$ with the following properties:For any threefold $Y$ of general type the number of dominant rational maps $f : X \to Y$ is bounded above by $c (X)$ .The number of threefolds $Y$ , modulo birational...

Examples of threefolds with Kodaira dimension 1 or 2

Alberto Calabri, Masaaki Murakami, Ezio Stagnaro (2011)

Rendiconti del Seminario Matematico della Università di Padova

Existence of Rank 3 Vector Bundles with Given Chern Classes on Homogeneous Rational 3-Folds.

C. Banica, Justin Coanda (1985)

Manuscripta mathematica

Explicit birational geometry of threefolds of general type, I

Jungkai A. Chen, Meng Chen (2010)

Annales scientifiques de l'École Normale Supérieure

Let $V$ be a complex nonsingular projective 3-fold of general type. We prove $P_{12} (V) : = dim H^{0} (V, 12 K_{V}) > 0$ and $P_{m_{0}} (V) > 1$ for some positive integer $m_{0} \leq 24$ . A direct consequence is the birationality of the pluricanonical map $ϕ_{m}$ for all $m \geq 126$ . Besides, the canonical volume $Vol (V)$ has a universal lower bound $ν (3) \geq \frac{1}{63 \cdot 126^{2}}$ .

Explicit reduction theory for Siegel modular threefolds.

Robert MacPherson, Mark McConnell (1993)

Inventiones mathematicae

Currently displaying 41 – 60 of 216

Previous Page 3 Next