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We address the following question: When an affine cone over a smooth Fano threefold admits an effective action of the additive group? In this paper we deal with Fano threefolds of index 1 and Picard number 1. Our approach is based on a…

Algebraic Geometry · Mathematics 2011-06-08 Takashi Kishimoto , Yuri Prokhorov , Mikhail Zaidenberg

We consider a smooth projective surjective morphism between smooth complex projective varieties. We give a Hodge theoretic proof of the following well-known fact: If the anti-canonical divisor of the source space is nef, then so is the…

Algebraic Geometry · Mathematics 2012-01-06 Osamu Fujino , Yoshinori Gongyo

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

We classify nef vector bundles on a projective space with first Chern class three over an algebraically closed field of characteristic zero; we see, in particular, that these nef vector bundles are globally generated if the second Chern…

Algebraic Geometry · Mathematics 2018-08-14 Masahiro Ohno

Following the work of Altmann and Hausen we give a combinatorial description in terms for smooth Fano threefolds admitting a 2-torus action. We show that a whole variety of properties and invariants can be read off from this description. As…

Algebraic Geometry · Mathematics 2018-10-11 Hendrik Süß

We give a classification of smooth Fano fourfolds such that the base scheme of the anticanonical system is a smooth surface. As a consequence we show that there are exactly 22 deformation families of such manifolds and they are all obtained…

Algebraic Geometry · Mathematics 2025-10-27 Andreas Höring , Saverio Andrea Secci

In this note we consider the problem of determining which Fano manifolds can be realised as fibres of a Mori fibre space. In particular, we study the case of toric varieties, Fano manifolds with high index and some Fano manifolds with high…

Algebraic Geometry · Mathematics 2022-11-08 Giulio Codogni , Andrea Fanelli , Roberto Svaldi , Luca Tasin

General expressions are given for Chern forms up to the 13th order in curvature in terms of simple polynomial concomitants of the curvature 2-form for n-dimensional differentiable manifolds having a general linear connection.

General Relativity and Quantum Cosmology · Physics 2007-05-23 C. C. Briggs

We provide enumerative formulas for the degrees of varieties parameterizing hypersurfaces and complete intersections which contain pro-jective subspaces and conics. Besides, we find all cases where the Fano scheme of the general complete…

Algebraic Geometry · Mathematics 2019-04-18 Ciro Ciliberto , M Zaidenberg

We classify rank two vector bundles on a Fano threefold of Picard rank one whose projectivizations are weak Fano. We also prove the existence of examples for each case of the classification result. Our classification includes detailed…

Algebraic Geometry · Mathematics 2025-05-07 Takeru Fukuoka , Wahei Hara , Daizo Ishikawa

The $c_1$-cohomological rigidity conjecture states that two smooth toric Fano varieties are isomorphic as varieties if there is a $c_1$-preserving isomorphism between their integral cohomology rings. In this paper, we confirm the conjecture…

Algebraic Geometry · Mathematics 2023-10-06 Yunhyung Cho , Eunjeong Lee , Mikiya Masuda , Seonjeong Park

We describe rank 2 Gieseker semistable sheaves $E$ on the Fano threefold $X_5$ of index 2 and degree 5 with maximal third Chern class $c_3(E)$ for all possible low values of discriminant $\overline{\Delta}_H(E)\le 40$. The work uses the…

Algebraic Geometry · Mathematics 2026-02-05 Danil A. Vassiliev

We give a necessary and sufficient condition for the nonsingular projective toric variety associated to the graph cubeahedron of a finite simple graph to be Fano or weak Fano in terms of the graph.

Algebraic Geometry · Mathematics 2018-04-30 Yusuke Suyama

Let $\mathcal{F}$ be a foliation on a projective manifold $X$ with $-K_{\mathcal{F}}$ nef. Assume that either $\mathcal{F}$ is regular, or it has a compact leaf. We prove that there is a locally trivial fibration $f\colon X\to Y$, and a…

Algebraic Geometry · Mathematics 2023-06-22 Wenhao Ou

In a previous paper it has been shown that the interference of the first and second order pole of the Green's function at an exceptional point, as well as the interference of the first order poles in the vicinity of the exceptional point,…

Quantum Physics · Physics 2015-12-04 Lukas Schwarz , Holger Cartarius , Günter Wunner , Walter Dieter Heiss , Jörg Main

We classify toric Fano threefolds having at worst terminal singularities such that a rank of a $G$-invariant part of a class group equals one, where $G$ is a group acting on the variety by automorphisms.

Algebraic Geometry · Mathematics 2022-09-05 Arman Sarikyan

We show that certain Fano eightfolds (obtained as hyperplane sections of an orthogonal Grassmannian, and studied by Ito-Miura-Okawa-Ueda and by Fatighenti-Mongardi) have a multiplicative Chow-K\"unneth decomposition. As a corollary, the…

Algebraic Geometry · Mathematics 2020-06-23 Robert Laterveer

As a special case of a conjecture by Schwede and Smith, we prove that a smooth complex projective threefold with nef anti-canonical divisor is weak Fano if it is of globally $F$-regular type.

Algebraic Geometry · Mathematics 2024-10-08 Paolo Cascini , Tatsuro Kawakami , Shunsuke Takagi

In this paper, we classify Fano fourfolds whose the second exterior power of tangent bundles are numerically effective with Picard number greater than one.

Algebraic Geometry · Mathematics 2014-01-14 Kazunori Yasutake

We classify the cones of curves of Fano varieties of dimension greater or equal than five and (pseudo)index dim X -3, describing the number and type of their extremal rays.

Algebraic Geometry · Mathematics 2017-09-29 Elena Chierici , Gianluca Occhetta