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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

In this paper, we introduce the notion of toric special weak Fano manifolds, which have only special primitive crepant contractions. We study the structure of them, and in particular completely classify smooth toric special weak Fano…

Algebraic Geometry · Mathematics 2021-05-26 Hiroshi Sato

We find all K-stable smooth Fano threefolds in the family No. 2.22.

Algebraic Geometry · Mathematics 2022-07-15 Ivan Cheltsov , Jihun Park

We characterize the birational geometry of some hyperk\"ahler fourfolds of Picard rank $3$ obtained as the Fano varieties of lines on cubic fourfolds containing pairs of cubic scrolls. In each of the two cases considered, we identify all of…

Algebraic Geometry · Mathematics 2025-09-10 Corey Brooke , Sarah Frei , Lisa Marquand , Xuqiang Qin

In a first result, we describe all finitely generated factorial algebras over an algebraically closed field of characteristic zero that come with an effective multigrading of complexity one by means of generators and relations. This enables…

Algebraic Geometry · Mathematics 2011-04-26 Juergen Hausen , Elaine Herppich , Hendrik Süß

We prove that if a smooth variety with non-positive canonical class can be embedded into a weighted projective space of dimension $n$ as a well formed complete intersection and it is not an intersection with a linear cone therein, then the…

Algebraic Geometry · Mathematics 2020-08-13 Victor Przyjalkowski , Constantin Shramov

We give a simple criterion for slope stability of Fano manifolds $X$ along divisors or smooth subvarieties. As an application, we show that $X$ is slope stable along an ample effective divisor $D\subset X$ unless $X$ is isomorphic to a…

Algebraic Geometry · Mathematics 2013-01-22 Kento Fujita

We compute the Hochschild-Kostant-Rosenberg decomposition of the Hochschild cohomology of Fano 3-folds. This is the first step in understanding the non-trivial Gerstenhaber algebra structure, and yields some initial insights in the…

Algebraic Geometry · Mathematics 2023-05-01 Pieter Belmans , Enrico Fatighenti , Fabio Tanturri

We define non-ordinary instanton bundles on Fano threefolds $X$ extending the notion of (ordinary) instanton bundles. We determine a lower bound for the quantum number of a non-ordinary instanton bundle, i.e. the degree of its second Chern…

Algebraic Geometry · Mathematics 2023-08-28 Vincenzo Antonelli , Gianfranco Casnati , Ozhan Genc

We study the cones of q-ample divisors on smooth complex varieties. In favourable cases, we identify a part where the closure of this cone and the nef cone have the same boundary. This is especially interesting for Fano (or almost Fano)…

Algebraic Geometry · Mathematics 2016-02-17 Robert Laterveer

We investigate the universal cover of projective threefolds whose tangent bundle is a direct sum of subbundles in case the Kodaira dimension is not 1 and 2. We also prove results on Fano manifolds with splitting tangent bundles in any…

Algebraic Geometry · Mathematics 2007-05-23 Frederic Campana , Thomas Peternell

We study Q-factorial terminal Fano 3-folds whose equations are modelled on those of the Segre embedding of P^2 x P^2. These lie in codimension 4 in their total anticanonical embedding and have Picard rank 2. They fit into the current state…

Algebraic Geometry · Mathematics 2021-12-17 Gavin Brown , Alexander Kasprzyk , Muhammad Imran Qureshi

We present a reconstruction theorem for Fano vector bundles on projective space which recovers the small quantum cohomology for the projectivisation of the bundle from a small number of low-degree Gromov--Witten invariants. We provide an…

Algebraic Geometry · Mathematics 2013-02-25 Andrew Strangeway

In this paper, we give a tropical method for computing Gromov-Witten type invariants of Fano manifolds of special type. This method applies to those Fano manifolds which admit toric degenerations to toric Fano varieties with singularities…

Algebraic Geometry · Mathematics 2010-01-19 Takeo Nishinou

This is not a research article. This is a partial version of a mini-cours which I gave at a meeting of the ACI Jeunes Chercheurs "Dynamique des applications polynomiales" in Toulouse in november 2004. This text includes two parts of that…

Algebraic Geometry · Mathematics 2007-05-23 Ekaterina Amerik

We develop an equivariant version of the Pfaffian-Grassmannian correspondence and apply it to produce examples of nontrivial twisted equivariant stable birationalities between cubic threefolds and degree 14 Fano threefolds.

Algebraic Geometry · Mathematics 2024-09-16 Yuri Tschinkel , Zhijia Zhang

This is a survey on the Fano schemes of linear spaces, conics, rational curves, and curves of higher genera in smooth projective hypersurfaces, complete intersections, Fano threefolds, etc.

Algebraic Geometry · Mathematics 2020-07-02 Ciro Ciliberto , Mikhail Zaidenberg

In this short note, we show that K-semistable Fano manifolds with the smallest alpha invariant are projective spaces. Singular cases are also investigated.

Algebraic Geometry · Mathematics 2017-11-27 Chen Jiang

We classify smooth Fano manifolds X with the Picard number $\rho_X \geq 3$ such that there exists an extremal ray which has a birational contraction that maps a divisor to a point.

Algebraic Geometry · Mathematics 2012-12-21 Kento Fujita

We generalize the equivariant intermediate Jacobian torsor obstruction over $\mathbb{C}$ to algebraically closed fields of characteristic zero. It is an obstruction to the (projective) linearizability problem of finite group actions on…

Algebraic Geometry · Mathematics 2026-01-13 Shuto Abe