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We classify Fano threefolds with only Gorenstein terminal singularities and Picard number greater than 1 satisfying an additional assumption that the $G$-invariant part of the Weil divisor class group is of rank 1 with respect to an action…

Algebraic Geometry · Mathematics 2016-01-29 Yuri Prokhorov

This paper obtains criteria for a Fano variety X with normal crossing singularities defined over an algebraically closed field of characteristic zero, to be smoothable. The difference with the original version is that the theory of…

Algebraic Geometry · Mathematics 2013-07-09 Nikolaos Tziolas

The 2-Fano varieties, defined by De Jong and Starr, satisfy some higher dimensional analogous properties of Fano varieties. We propose a definition of (weak) $k$-Fano variety and conjecture the polyhedrality of the cone of pseudoeffective…

Algebraic Geometry · Mathematics 2024-08-02 Giosuè Emanuele Muratore

Given a seven-element set $X = \{1,2,3,4,5,6,7\}$, there are 30 ways to define a Fano plane on it. Let us call a line of such Fano plane, that is to say an unordered triple from $X$, ordinary or defective according as the sum of two smaller…

Combinatorics · Mathematics 2016-08-24 Metod Saniga

We consider some families of smooth Fano hypersurfaces $X_{n+2}$ in ${\bf P}^{n+2} \times {\bf P}^3$ given by a homogeneous polynomial of bidegree $(1,3)$. For these varieties we obtain lower bounds for the number of $F$-rational points of…

alg-geom · Mathematics 2008-02-03 Victor V. Batyrev , Yuri Tschinkel

Iterating the procedure of making a double cover over a given variety, we construct large families of smooth higher-dimensional Fano varieties of index 1. These varieties can be realized as complete intersections in various weighted…

Algebraic Geometry · Mathematics 2015-06-26 Aleksandr V. Pukhlikov

According to Mukai, any prime Fano threefold X of genus 7 is a linear section of the spinor tenfold in the projectivized half-spinor space of Spin(10). It is proven that the moduli space of stable rank-2 vector bundles with Chern classes…

Algebraic Geometry · Mathematics 2007-05-23 A. Iliev , D. Markushevich

We study varieties of complexes of projective modules with fixed ranks, and relate these varieties to the varieties of their homologies. We show that for an algebra of global dimension at most two, these two varieties are related by a pair…

Representation Theory · Mathematics 2014-10-02 Darmajid , Bernt Tore Jensen

We give a self-contained and simplified proof of Mukai's classification of prime Fano threefolds of index 1 and genus $g \ge 6$ with at most Gorenstein factorial terminal singularities, and of its extension to higher-dimension.

Algebraic Geometry · Mathematics 2025-07-01 Arend Bayer , Alexander Kuznetsov , Emanuele Macrì

Let X be a smooth complex Fano variety. We define and study 'quasi elementary' contractions of fiber type f: X -> Y. These have the property that rho(X) is at most rho(Y)+rho(F), where rho is the Picard number and F is a general fiber of f.…

Algebraic Geometry · Mathematics 2008-04-18 C. Casagrande

We study Fano 3-folds with Fano index 2: that is, 3-folds X with rank Pic(X) = 1, Q-factorial terminal singularities and -K_X = 2A for an ample Weil divisor A. We give a first classification of all possible Hilbert series of such polarised…

Algebraic Geometry · Mathematics 2007-05-23 Gavin Brown , Kaori Suzuki

We prove that the Fano variety of lines of a cuspidal cyclic cubic fourfold is a symplectic variety with transversal A2-singularities and we study the properties of the nonsymplectic order three automorphism induced by the covering…

Algebraic Geometry · Mathematics 2023-03-28 Samuel Boissiere , Tobias Heckel , Alessandra Sarti

We introduce a new subclass of Fano varieties (Casagrande-Druel varieties), that are $n$-dimensional varieties constructed from Fano double covers of dimension $n-1$. We conjecture that a Casagrande-Druel variety is K-polystable if the…

Algebraic Geometry · Mathematics 2023-09-25 Ivan Cheltsov , Tiago Duarte Guerreiro , Kento Fujita , Igor Krylov , Jesus Martinez-Garcia

We classify primitive Fano threefolds in positive characteristic whose Picard numbers are at least two. We also classify Fano theefolds of Picard rank two.

Algebraic Geometry · Mathematics 2025-07-24 Masaya Asai , Hiromu Tanaka

It is shown that hypersurfaces of degree $M$ in ${\mathbb P}^M$, $M\geqslant 5$, with at most quadratic singularities of rank at least 3, satisfying certain conditions of general position, are birationally superrigid Fano varieties and the…

Algebraic Geometry · Mathematics 2023-12-29 Aleksandr V. Pukhlikov

We study three-dimensional Fano varieties with $\mathbb{C}^*$-action. Complementing recent results [13], we give classification results in the canonical case, where the maximal orbit quotient is $\mathbb{P}_2$ having a line arrangement of…

Algebraic Geometry · Mathematics 2019-12-18 Christoff Hische , Milena Wrobel

We prove LeBrun--Salamon conjecture in the following situation: if $X$ is a contact Fano manifold of dimension $2n+1$ whose group of automorphisms is reductive of rank $\geq \max(2,(n-3)/2)$ then $X$ is the adjoint variety of a simple…

Algebraic Geometry · Mathematics 2021-03-15 Gianluca Occhetta , Eleonora A. Romano , Luis E. Solá Conde , Jarosław A. Wiśniewski

The classification of toric Fano manifolds with large Picard number corresponds to the classification of smooth Fano polytopes with large number of vertices. A smooth Fano polytope is a polytope that contains the origin in its interior such…

Algebraic Geometry · Mathematics 2015-08-11 Benjamin Assarf , Benjamin Nill

We classify some special classes of non-rational Fano threefolds with terminal singularities. In particular, all such hyperelliptic and trigonal varieties are found.

Algebraic Geometry · Mathematics 2019-07-15 Yuri Prokhorov

Conjecturally, Fano varieties of K3 type admit a multiplicative Chow-K\"unneth decomposition, in the sense of Shen-Vial. We prove this for many of the families of Fano varieties of K3 type constructed by Fatighenti-Mongardi. This has…

Algebraic Geometry · Mathematics 2021-08-20 Robert Laterveer