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We classify Fano threefolds with only terminal singularities whose canonical class is Cartier and divisible by 2, and satisfying an additional assumption that the $G$-invariant part of the Weil divisor class group is of rank 1 with respect…

Algebraic Geometry · Mathematics 2013-08-06 Yuri Prokhorov

We study rational curves on general Fano hypersurfaces in projective space, mostly by degenerating the hypersurface along with its ambient projective space to reducible varieties. We prove results on existence of low-degree rational curves…

Algebraic Geometry · Mathematics 2020-03-11 Ziv Ran

We prove that $\mathbb{Q}$-Fano threefolds of Fano index $\ge 8$ are rational.

Algebraic Geometry · Mathematics 2019-03-19 Yuri Prokhorov

We prove a characterization of Fano type varieties.

Algebraic Geometry · Mathematics 2026-03-17 Yiming Zhu

We extend results of Chang and Ran regarding large dimensional families of immersed curves of positive genus in projective space in two directions. In one direction, we prove a sharp bound for the dimension of a complete family of smooth…

Algebraic Geometry · Mathematics 2019-02-01 Dennis Tseng

Hilbert curves of special varieties like Fano manifolds of low coindex as well as fibrations having such a manifold as general fiber, endowed with appropriate polarizations, are investigated. In particular, all most relevant varieties…

Algebraic Geometry · Mathematics 2018-03-06 Antonio Lanteri , Andrea Luigi Tironi

We classify families of free rational curves on all smooth Fano threefolds over the complex numbers. In particular, we prove the family of very free rational curves representing any fixed numerical curve class is either irreducible or…

Algebraic Geometry · Mathematics 2024-09-04 Andrew Burke , Eric Jovinelly

We construct 4 di erent families of smooth Fano fourfolds with Picard rank 1, which contain cylinders, i.e., Zariski open subsets of the form Z x A1, where Z is a quasiprojective variety. The affi ne cones over such a fourfold admit eff…

Algebraic Geometry · Mathematics 2014-06-25 Yuri Prokhorov , Mikhail Zaidenberg

We consider weak Fano manifolds with small contractions obtained by blowing up successively curves and subvarieties of codimension 2 in products of projective spaces. We give a classification result for a special case. In the process of…

Algebraic Geometry · Mathematics 2016-10-25 Toru Tsukioka

A Fano manifold $X$ with nef tangent bundle is of flag-type if it has the same type of elementary contractions as a complete flag manifold. In this paper we present a method to associate a Dynkin diagram $\mathcal{D}(X)$ with any such $X$,…

Algebraic Geometry · Mathematics 2015-03-18 Roberto Muñoz , Gianluca Occhetta , Luis Eduardo Solá Conde , Kiwamu Watanabe

A V_{12} Fano threefold is a smooth Fano threefold X of index 1 with Pic X = Z and (-K_X)^3=12. We show that the bounded derived category of coherent sheaves on any V_{12} threefold X admits a semiorthogonal decomposition consisting of two…

Algebraic Geometry · Mathematics 2007-05-23 Alexander Kuznetsov

On a general Fano hypersurface in projective space, we determine for infinitely many $k$ the minimal degree $e$ of a rational curve through a general collection of $k$ points. In the case of a hypersurface of index 1, our results hold for…

Algebraic Geometry · Mathematics 2021-12-28 Ziv Ran

In this paper we prove that a regular foliation on a complex weak Fano manifold is algebraically integrable.

Algebraic Geometry · Mathematics 2015-10-19 Stéphane Druel

Curves of low genus on a surface carry important informations on that surface. We study the Fano surfaces of lines of cubic threefolds that contain 12 or 30 elliptic curves. We determine their Picard number and compute a basis of the…

Algebraic Geometry · Mathematics 2010-02-05 Xavier Roulleau

We classify Fano 3-folds with canonical Gorenstein singularities whose anticanonical linear system has no base points but does not give an embedding, and we classify anticanonically embedded Fano 3-folds with canonical Gorenstein…

Algebraic Geometry · Mathematics 2007-05-23 Ivan Cheltsov , Constantin Shramov , Victor Przyjalkowski

We describe the moduli space of rational curves on smooth Fano varieties of coindex 3. For varieties of dimension 5 or greater, we prove the moduli space has a single irreducible component for each effective numerical class of curves. For…

Algebraic Geometry · Mathematics 2024-09-04 Eric Jovinelly , Fumiya Okamura

General linear sections of codimension 2 of the Grassmannians G(1,4) and G(1,5) appear in the classification of Fano manifolds of high index. Unlike Grassmannians, these manifolds are not homogeneous. Nevertheless, their automorphisms…

Algebraic Geometry · Mathematics 2015-05-26 Rafael Lucas de Arruda

The goal of this article is to study the equations and syzygies of embeddings of rational surfaces and certain Fano varieties. Given a rational surface X and an ample and base-point-free line bundle L on X, we give an optimal numerical…

Algebraic Geometry · Mathematics 2007-05-23 Francisco Javier Gallego , B. P. Purnaprajna

We classify compact K\"ahler manifolds with semi-positive holomorphic bisectional and big tangent bundles. We also classify compact complex surfaces with semi-positive tangent bundles and compact complex $3$-folds of the form $P(T^*X)$…

Differential Geometry · Mathematics 2015-04-24 Xiaokui Yang

Let $X \subset \mathbb{P}^n$ be a general Fano complete intersection of type $(d_1,\dots, d_k)$. If at least one $d_i$ is greater than $2$, we show that $X$ contains rational curves of degree $e \leq n$ with balanced normal bundle. If all…

Algebraic Geometry · Mathematics 2017-05-24 Izzet Coskun , Eric Riedl