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We study a wide class of affine varieties, which we call affine Fano varieties. By analogy with birationally super-rigid Fano varieties, we define super-rigidity for affine Fano varieties, and provide many examples and non-examples of…

Algebraic Geometry · Mathematics 2019-02-20 Ivan Cheltsov , Adrien Dubouloz , Jihun Park

We completely describe the Fano scheme of lines for a projective toric surface in terms of the geometry of the corresponding lattice polygon.

Algebraic Geometry · Mathematics 2019-11-26 Nathan Ilten

This paper is a survey about cylinders in Fano varieties and related problems.

Algebraic Geometry · Mathematics 2021-05-11 Ivan Cheltsov , Jihun Park , Yuri Prokhorov , Mikhail Zaidenberg

Rationality is not a constructible property in families. In this article, we consider stronger notions of rationality and study their behavior in families of Fano varieties. We first show that being toric is a constructible property in…

Algebraic Geometry · Mathematics 2025-09-29 Lena Ji , Joaquín Moraga

One can associate to a bipartite graph a so-called edge ring whose spectrum is an affine normal toric variety. We characterize the faces of the (edge) cone associated to this toric variety in terms of some independent sets of the bipartite…

Algebraic Geometry · Mathematics 2020-09-15 Irem Portakal

We give an effective upper bound for the index of klt complements on toric Fano varieties.

Algebraic Geometry · Mathematics 2025-07-30 Florin Ambro

A vector bundle whose projectivization becomes a weak Fano variety is called a weak Fano bundle. We present classification results for rank 2 weak Fano bundles on higher-dimensional quadrics $Q^n$ of dimension $\ge 5$.

Algebraic Geometry · Mathematics 2025-01-22 Yuta Takahashi

We prove that the Fano variety of lines of a generic cubic fourfold containing a plane is isomorphic to a moduli space of twisted stable complexes on a K3 surface. On the other hand, we show that the Fano varieties are always birational to…

Algebraic Geometry · Mathematics 2011-12-26 Emanuele Macri , Paolo Stellari

A simple algebraic characterization of the Fano manifolds in the class of homogeneous toric bundles over a flag manifold $G^C/P$ is provided in terms of symplectic data.

Differential Geometry · Mathematics 2007-05-23 Fabio Podesta' , Andrea Spiro

In this paper we construct a spectral sequence computing a modified version of morphic cohomology of a toric variety (even when it is singular) in terms of combinatorial data coming from the fan of the toric variety.

Algebraic Geometry · Mathematics 2010-01-19 Abdó Roig-Maranges

We provide a systematic method to classify all smooth weak Fano toric varieties of Picard rank $3$ in any dimension using Macaulay2, and describe the classification explicitly in dimensions $3$ and $4$. There are $28$ and $114$ isomorphism…

Algebraic Geometry · Mathematics 2025-06-03 Zhengning Hu , Rohan Joshi

We study the Picard variety of the Fano surface of nodal and mildly cuspidal cubic threefolds in arbitrary characteristic by relating divisors on the Fano surface to divisors on the symmetric product of a curve of genus 4.

Algebraic Geometry · Mathematics 2010-10-12 Gerard van der Geer , Alexis Kouvidakis

We classify $2$-Fano horospherical varieties with Picard number $1$. We also review all the known examples of $2$-Fano manifolds and investigate the relation between the $2$-Fano condition and different notions of stability. This paper was…

Algebraic Geometry · Mathematics 2023-12-21 Carolina Araujo , Ana-Maria Castravet

We give the first examples of flat fiber type contractions of Fano manifolds onto varieties that are not weak Fano, and we prove that these morphisms are Fano conic bundles. We also review some known results about the interaction between…

Algebraic Geometry · Mathematics 2017-03-09 Eleonora Anna Romano

In this paper we explain the complete biregular classification of all 4-dimensional smooth toric Fano varieties. The main result states that there exist exactly 123 different types of toric Fano 4-folds up to isomorphism.

Algebraic Geometry · Mathematics 2007-05-23 Victor V. Batyrev

We list combinatorial criteria of some singularities, which appear in the Minimal Model Program or in the study of (singular) Fano varieties, for spherical varieties. Most of the results of this paper are already known or are quite easy…

Algebraic Geometry · Mathematics 2015-10-15 Boris Pasquier

It is pretty well-known that toric Fano varieties of dimension k with terminal singularities correspond to convex lattice polytopes P in R^k of positive finite volume, such that intersection of P and Z^k consists of the point 0 and vertices…

Algebraic Geometry · Mathematics 2007-05-23 Alexandr Borisov

We consider a smooth projective morphism between smooth complex projective varieties. If the source space is a weak Fano (or Fano) manifold, then so is the target space. Our proof is Hodge theoretic. We do not need mod $p$ reduction…

Algebraic Geometry · Mathematics 2010-05-03 Osamu Fujino , Yoshinori Gongyo

A horospherical variety is a normal algebraic variety where a reductive algebraic group acts with an open orbit which is a torus bundle over a flag variety. For example, toric varieties and flag varieties are horospherical. In this paper,…

Algebraic Geometry · Mathematics 2007-05-23 Boris Pasquier

The aim of this note is to settle some foundational questions about the behavior of birational rigidity in extensions of algebraically closed fields.

Algebraic Geometry · Mathematics 2008-09-08 János Kollár