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We provide a systematic method to classify all smooth weak Fano toric varieties of Picard rank $3$ in any dimension using Macaulay2, and describe the classification explicitly in dimensions $3$ and $4$. There are $28$ and $114$ isomorphism…

Algebraic Geometry · Mathematics 2025-06-03 Zhengning Hu , Rohan Joshi

Let X be a complex Fano manifold of arbitrary dimension, and D a prime divisor in X. We consider the image H of N_1(D) in N_1(X) under the natural push-forward of 1-cycles. We show that the codimension c of H in N_1(X) is at most 8.…

Algebraic Geometry · Mathematics 2011-12-21 C. Casagrande

For a toric variety X_P determined by a rational polyhedral fan P in a lattice N, Payne shows that the equivariant Chow cohomology of X_P is the Sym(N)--algebra C^0(P) of integral piecewise polynomial functions on P. We use the…

Algebraic Geometry · Mathematics 2014-07-14 Hal Schenck

In this paper we extend to the singular setting the theory of Fano foliations developed in our previous paper. A Q-Fano foliation on a complex projective variety X is a foliation F whose anti-canonical class is an ample Q-Cartier divisor.…

Algebraic Geometry · Mathematics 2014-04-16 Carolina Araujo , Stéphane Druel

We show that for a K-unstable Fano variety, any divisorial valuation computing its stability threshold induces a non-trivial special test configuration preserving the stability threshold. When such a divisorial valuation exists, we show…

Algebraic Geometry · Mathematics 2022-12-21 Harold Blum , Yuchen Liu , Chuyu Zhou

In the paper "Birational geometry via moduli spaces" by I. Cheltsov, L. Katzarkov, and V. Przyjalkowski a new structure connecting toric degenerations of smooth Fano threefolds by projections was introduced; using Mirror Symmetry these…

Algebraic Geometry · Mathematics 2019-04-05 Alexander Kasprzyk , Ludmil Katzarkov , Victor Przyjalkowski , Dmitrijs Sakovics

We construct degenerations of Mukai varieties and linear sections thereof to special unobstructed Fano Stanley-Reisner schemes corresponding to convex deltahedra. This can be used to find toric degenerations of rank one index one Fano…

Algebraic Geometry · Mathematics 2019-11-26 Jan Arthur Christophersen , Nathan Owen Ilten

Let $X$ be a cubic fourfold that has only simple singularities and does not contain a plane. We prove that the Fano variety of lines on $X$ has the same analytic type of singularity as the Hilbert scheme of two points on a surface with only…

Algebraic Geometry · Mathematics 2018-04-03 Ryo Yamagishi

We study the varieties of reductions associated to the variety of rank one matrices in $\fgl\_n$. These varieties are defined as natural compactifications of the different ways to write the identity matrix as a sum of $n$ rank one matrices.…

Algebraic Geometry · Mathematics 2008-10-15 Atanas Iliev , Laurent Manivel

Suppose that X is a Fano manifold that corresponds under Mirror Symmetry to a Laurent polynomial f, and that P is the Newton polytope of f. In this setting it is expected that there is a family of algebraic varieties over the unit disc with…

Algebraic Geometry · Mathematics 2019-12-11 Tom Coates , Alessio Corti , Genival da Silva

We classify nonrational Fano threefolds $X$ with terminal Gorenstein singularities such that $\mathrm{\rk}\, \mathrm{\Pic}(X)=1$, $(-K_X)^3\ge 8$, and $\mathrm{\rk}\, \mathrm{\Cl}(X)\le 2$.

Algebraic Geometry · Mathematics 2022-05-18 Yuri Prokhorov

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 prove divisorial canonicity of Fano double hypersurfaces of general position.

Algebraic Geometry · Mathematics 2009-11-13 Aleksandr Pukhlikov

A normal projective variety X is called Fano if a multiple of the anticanonical Weil divisor, -K_X, is an ample Cartier divisor, the index of a Fano variety is the number i(X):=sup{t: -K_X= tH, for some ample Cartier divisor H}. Mukai…

alg-geom · Mathematics 2008-02-03 Massimiliano Mella

We construct first examples of Fano varieties with torsion in their third cohomology group. The examples are constructed as double covers of linear sections of rank loci of symmetric matrices, and can be seen as higher-dimensional analogues…

Algebraic Geometry · Mathematics 2023-11-17 John Christian Ottem , Jørgen Vold Rennemo

We prove that the derived category of a smooth complete intersection variety is equivalent to a full subcategory of the derived category of a smooth projective Fano variety. This enables us to define some new invariants of smooth projective…

Algebraic Geometry · Mathematics 2015-04-30 Young-Hoon Kiem , In-Kyun Kim , Hwayoung Lee , Kyoung-Seog Lee

We study birational geometry of Fano varieties, realized as double covers $\sigma\colon V\to {\mathbb P}^M$, $M\geq 5$, branched over generic hypersurfaces $W=W_{2(M-1)}$ of degree $2(M-1)$. We prove that the only structures of a rationally…

Algebraic Geometry · Mathematics 2009-05-22 Aleksandr Pukhlikov

Let $X \subset \mathbb{P}^{n+1}$ be a smooth Fano hypersurface of dimension $n$ and degree $d$. The derived category of coherent sheaves on $X$ contains an interesting subcategory called the Kuznetsov component $\mathcal{A}_X$. We show that…

Algebraic Geometry · Mathematics 2022-08-30 Dmitrii Pirozhkov

We generalized the construction of deformations of affine toric varieties of K. Altmann and our previous construction of deformations of weak Fano toric varieties to the case of arbitrary toric varieties by introducing the notion of…

Algebraic Geometry · Mathematics 2011-02-25 Anvar Mavlyutov

It is known that there are only finitely many mutation-equivalence classes with a given singularity content, and each of these equivalence classes contains only finitely many minimal polygons. We describe an efficient algorithm to classify…

Algebraic Geometry · Mathematics 2017-03-16 Daniel Cavey , Edwin Kutas