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We initiate the study of finite abelian groups that faithfully act on 3-dimensional rationally connected varieties. We show that these groups can be naturally divided into three types: the groups of product type are finite abelian groups…

Algebraic Geometry · Mathematics 2025-01-03 Konstantin Loginov

Fano varieties are 'atomic pieces' of algebraic varieties, the shapes that can be defined by polynomial equations. We describe the role of computation and database methods in the construction and classification of Fano varieties, with an…

Algebraic Geometry · Mathematics 2022-11-21 Gavin Brown , Tom Coates , Alessio Corti , Tom Ducat , Liana Heuberger , Alexander Kasprzyk

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

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

This paper is concerned with a sufficient criterion to guarantee that a given foliation on a normal variety has algebraic and rationally connected leaves. Following ideas from a preprint of Bogomolov-McQuillan and using recent works of…

Algebraic Geometry · Mathematics 2009-09-29 Stefan Kebekus , Luis Sola Conde , Matei Toma

We study a particular kind of fiber type contractions between complex, projective, smooth varieties f:X->Y, called Fano conic bundles. This means that X is a Fano variety, and every fiber of f is isomorphic to a plane conic. Denoting by…

Algebraic Geometry · Mathematics 2018-03-15 Eleonora Anna Romano

We prove that very general non-rational Fano threefolds which are not birational to cubic threefolds are not stably rational.

Algebraic Geometry · Mathematics 2016-01-27 Brendan Hassett , Yuri Tschinkel

In this paper I study the rationality problem for Fano threefolds $X\subset \p^{p+1}$ of genus $p$, that are Gorenstein, with at most canonical singularities. The main results are: (1) a trigonal Fano threefold of genus $p$ is rational as…

Algebraic Geometry · Mathematics 2023-06-08 Ciro Ciliberto

We construct $S$-linear semiorthogonal decompositions of derived categories of smooth Fano threefold fibrations $X/S$ with relative Picard rank $1$ and rational geometric fibers and discuss how the structure of components of these…

Algebraic Geometry · Mathematics 2022-10-03 Alexander Kuznetsov

In this paper we consider certain closed subvarieties of the flag variety, known as Hessenberg varieties. We give a connectedness criterion for semisimple Hessenberg varieties generalizing a criterion given by Anderson and Tymoczko. We show…

Algebraic Geometry · Mathematics 2013-10-17 Martha Precup

The aim of this work is to provide the first examples of $n$-dimensional varieties of wild representation type, for arbitrary $n\geq 2$. More precisely, we prove that all Fano blow-ups of $\PP^n$ at a finite number of points are of wild…

Algebraic Geometry · Mathematics 2010-11-17 Rosa M. Miró-Roig Joan Pons-Llopis

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

For $n\geq 4$, let $X$ be a complex smooth Fano $n$-fold whose minimal anticanonical degree of non-free rational curves on $X$ is at least $n-2$. We classify extremal contractions of such varieties. As an application, we obtain a…

Algebraic Geometry · Mathematics 2024-06-04 Kiwamu Watanabe

This is a survey paper about a selection of recent results on the geometry of a special class of Fano varieties, which are called of K3 type. The focus is mostly Hodge-theoretical, with an eye towards the multiple connections between Fano…

Algebraic Geometry · Mathematics 2022-06-14 Enrico Fatighenti

We prove the $W\mathcal{O}$-rationality of klt threefolds and the rational chain connectedness of klt Fano threefolds over a perfect field of characteristic $p>5$. As a consequence, any klt Fano threefold over a finite field has a rational…

Algebraic Geometry · Mathematics 2016-12-01 Yoshinori Gongyo , Yusuke Nakamura , Hiromu Tanaka

For Fano-Mori fibre spaces $\pi\colon V\to S$, every fibre of which is a primitive Fano variety with the global canonical threshold at least 1, and which are stable with respect to birational modifications of the base and sufficiently…

Algebraic Geometry · Mathematics 2023-11-21 Aleksandr V. Pukhlikov

We establish a conjecture of Mumford characterizing rationally connected complex projective manifolds in several cases.

Algebraic Geometry · Mathematics 2017-05-05 Vladimir Lazić , Thomas Peternell

We construct exceptional Fano varieties with the smallest known minimal log discrepancies in all dimensions. These varieties are well-formed hypersurfaces in weighted projective space. Their minimal log discrepancies decay doubly…

Algebraic Geometry · Mathematics 2024-06-07 Louis Esser , Jihao Liu , Chengxi Wang

We show that the degrees of rational endomorphisms of very general complex Fano and Calabi-Yau hypersurfaces satisfy certain congruence conditions by specializing to characteristic p. As a corollary we show that very general n-dimensional…

Algebraic Geometry · Mathematics 2022-05-20 Nathan Chen , David Stapleton

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