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We describe the closed cone of moving curves of smooth Fano three- and fourfolds by giving finitely many equations that cut out the cone. The equations are induced by the exceptional divisors of divisorial contractions and by nef divisors…

Algebraic Geometry · Mathematics 2009-02-03 Sammy Barkowski

Explicit birational geometry of 3-folds represents a second phase of Mori theory, going beyond the foundational work of the 1980s. This paper is a tutorial and colloquial introduction to the explicit classification of Fano 3-folds (Q-Fano…

Algebraic Geometry · Mathematics 2007-05-23 Selma Altınok , Gavin Brown , Miles Reid

This paper was written in 1982. Ideas and methods of "Clemens C.H., Griffiths Ph. The intermediate Jacobian of a cubic threefold" are applied to a Fano threefold X of genus 6 -- intersection of Grassmann sixfold with two hyperplanes and a…

Algebraic Geometry · Mathematics 2007-05-23 Dmitry Logachev

This paper gives sharp linear bounds on the genus of a normal surface in a triangulated compact, orientable 3--manifold in terms of the quadrilaterals in its cell decomposition---different bounds arise from varying hypotheses on the surface…

Geometric Topology · Mathematics 2016-07-20 William Jaco , Jesse Johnson , Jonathan Spreer , Stephan Tillmann

In this note we study Fano threefolds with noncyclic torsion in the divisor class group. Since they can all be obtained as quotients of Fano threefolds, we get also all examples that can be obtained as quotients of low codimension Fanos in…

Algebraic Geometry · Mathematics 2007-06-14 Jorge Caravantes

We show that mixed-characteristic and equi-characteristic small deformations of 3-dimensional canonical (resp. terminal) singularities with perfect residue field of characteristic $p>5$ are canonical (resp. terminal). We discuss…

Algebraic Geometry · Mathematics 2024-03-08 Fabio Bernasconi , Iacopo Brivio , Stefano Filipazzi

This note is about cycle-theoretic properties of the Fano variety of lines on a smooth cubic fivefold. The arguments are based on the fact that this Fano variety has finite-dimensional motive. We also present some results concerning Chow…

Algebraic Geometry · Mathematics 2017-06-20 Robert Laterveer

There have been major developments in the theory of moduli of varieties in the past decade, essentially settling the construction of moduli spaces of log canonically polarized slc pairs and moduli spaces of K-polystable log Fano pairs.…

Algebraic Geometry · Mathematics 2026-02-25 Kristin DeVleming

We construct Fano threefolds with very ample anti-canonical bundle and Picard rank greater than one from cracked polytopes - polytopes whose intersection with a complete fan forms a set of unimodular polytopes - using Laurent inversion; a…

Algebraic Geometry · Mathematics 2019-07-30 Thomas Prince

We announce a factorization result for equivariant birational morphisms between toric 4-folds whose source is Fano: such a morphism is always a composite of blow-ups along smooth invariant centers. Moreover, we show with a counterexample…

Algebraic Geometry · Mathematics 2007-05-23 Cinzia Casagrande

First the title could be also understood as ``3-manifolds related by non-zero degree maps" or "Degrees of maps between 3-manifolds" for some aspects in this survey talk. The topology of surfaces was completely understood at the end of 19th…

Geometric Topology · Mathematics 2007-05-23 Shicheng Wang

We prove finiteness of the number of smooth blow-downs on Fano manifolds and boundedness results for the geometry of non projective Fano-like manifolds. Our proofs use properness of Hilbert schemes and Mori theory.

Algebraic Geometry · Mathematics 2007-05-23 L. Bonavero , S. Takayama

We find new lower bounds on the torsion orders of very general Fano hypersurfaces over (uncountable) fields of arbitrary characteristic. Our results imply that unirational parametrizations of most Fano hypersurfaces need to have enormously…

Algebraic Geometry · Mathematics 2021-03-03 Stefan Schreieder

The purpose of this paper is to compute the degree of irrationality of hypersurfaces of sufficiently high degree in various Fano varieties: quadrics, Grassmannians, products of projective space, cubic threefolds, cubic fourfolds, and…

Algebraic Geometry · Mathematics 2018-03-09 David Stapleton , Brooke Ullery

We introduce a concept of minimality for Fano polygons. We show that, up to mutation, there are only finitely many Fano polygons with given singularity content, and give an algorithm to determine the mutation-equivalence classes of such…

Algebraic Geometry · Mathematics 2022-10-28 Alexander Kasprzyk , Benjamin Nill , Thomas Prince

We prove that Generalized Mukai Conjecture holds for Fano manifolds $X$ of pseudoindex $i_X \ge (\dim X +3)/3$. We also give different proofs of the conjecture for Fano fourfolds and fivefolds.

Algebraic Geometry · Mathematics 2009-12-14 Carla Novelli , Gianluca Occhetta

Small codimensional embedded manifolds defined by equations of small degree are Fano and covered by lines. They are complete intersections exactly when the variety of lines through a general point is so and has the right codimension. This…

Algebraic Geometry · Mathematics 2012-09-11 Paltin Ionescu , Francesco Russo

In 1949 Fano published his last paper on $3$-folds with canonical sectional curves. There he constructed and described a $3$-fold of the type $X^{22}_3$ in ${\mathbb P}^{13}$ with canonical curve section, which we like to call Fano's last…

Algebraic Geometry · Mathematics 2022-12-20 Marco Andreatta , Roberto Pignatelli

The main purpose of this article is to prove that the family of all Fano threefolds with log-terminal singularities with bounded index is bounded.

alg-geom · Mathematics 2008-02-03 A. Borisov

Let $X$ be a projective variety and let $C$ be a rational normal curve on $X$. We compute the normal bundle of $C$ in a general complete intersection of hypersurfaces of sufficiently large degree in $X$. As a result, we establish the…

Algebraic Geometry · Mathematics 2021-06-04 Izzet Coskun , Geoffrey Smith