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Let $X$ be a Fano type variety and $(X,\Delta)$ be a log Calabi-Yau pair with $\Delta$ a Weil divisor. If $(X,\Delta)$ admits a polarized endomorphism, then we show that $(X,\Delta)$ is a finite quotient of a toric pair. Along the way, we…

Algebraic Geometry · Mathematics 2024-03-14 Joaquín Moraga , José Ignacio Yáñez , Wern Yeong

Let $X$ be a Fano variety with at worst isolated quotient singularities. Our result asserts that if $C \cdot (-K_X) > max\{\frac{n}{2}+1,\frac{2n}{3}\}$ for every curve $C \subset X$, then $\rho_X=1$.

Algebraic Geometry · Mathematics 2009-10-29 Jiun-Cheng Chen

Let $X$ be an $n$-dimensional normal $\mathbb{Q}$-factorial projective variety with canonical singularities and Picard number one such that $X$ is smooth in codimension two, $-K_X$ is ample and $n\geq 2$. We prove that $X$ satisfies the…

Algebraic Geometry · Mathematics 2024-11-28 Haidong Liu , Jie Liu

Complete intersections inside rational homogeneous varieties provide interesting examples of Fano manifolds. For example, if $X = \cap_{i=1}^r D_i \subset G/P$ is a general complete intersection of $r$ ample divisors such that $K_{G/P}^*…

Algebraic Geometry · Mathematics 2018-08-07 Chenyu Bai , Baohua Fu , Laurent Manivel

In this paper we classify n-dimensional Fano manifolds with index >=n-2 and positive second Chern character.

Algebraic Geometry · Mathematics 2012-06-08 Carolina Araujo , Ana-Maria Castravet

Let $X$ be a smooth Fano threefold. We show that $X$ admits a non-isomorphic surjective endomorphism if and only if $X$ is either a toric variety or a product of $\mathbb{P}^1$ and a del Pezzo surface; in this case, $X$ is a rational…

Algebraic Geometry · Mathematics 2022-08-11 Sheng Meng , De-Qi Zhang , Guolei Zhong

We prove the birational rigidity of Fano complete intersections of index 1 with a singular point of high multiplicity, which can be close to the degree of the variety. In particular, the groups of birational and biregular automorphisms of…

Algebraic Geometry · Mathematics 2017-11-07 Aleksandr V. Pukhlikov

Let X be a Fano manifold with Picard number one such that the tangent bundle T_X is big. If X admits a rational curve with trivial normal bundle, we show that X is isomorphic to the del Pezzo threefold of degree five.

Algebraic Geometry · Mathematics 2021-10-15 Andreas Höring , Jie Liu

Let $f\colon X\to Y$ be a surjective morphism of Fano manifolds of Picard number 1 whose VMRTs at a general point are not dual defective. Suppose that the tangent bundle $T_X$ is big. We show that $f$ is an isomorphism unless $Y$ is a…

Algebraic Geometry · Mathematics 2024-07-30 Feng Shao , Guolei Zhong

We construct a family of examples of Legendrian subvarieties in some projective spaces. Although most of them are singular, a new example of smooth Legendrian variety in dimension 8 is in this family. The 8-fold has interesting properties:…

Algebraic Geometry · Mathematics 2010-01-20 Jaroslaw Buczynski

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 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 Picard rank is constant in families of Fano varieties (in arbitrary characteristic) and we moreover investigate the constancy of the index.

Algebraic Geometry · Mathematics 2017-04-12 Frank Gounelas , Ariyan Javanpeykar

Let $X$ be a smooth Fano fourfold admitting a conic bundle structure. We show that $X$ is toric if and only if $X$ admits an amplified endomorphism; in this case, $X$ is a rational variety.

Algebraic Geometry · Mathematics 2023-09-06 Jia Jia , Guolei Zhong

We classify the terminal Fano threefolds of Picard number one that come with an effective action of a two-torus. Our approach applies also to higher dimensions and generalizes the correspondence between toric Fano varieties and lattice…

Algebraic Geometry · Mathematics 2025-07-08 Benjamin Bechtold , Elaine Huggenberger , Juergen Hausen , Michele Nicolussi

Let X be a normal variety such that $K_X$ is Q-Cartier, and let $f: X \rightarrow X$ be a finite surjective morphism of degree at least two. We establish a close relation between the irreducible components of the locus of singularities that…

Algebraic Geometry · Mathematics 2017-10-30 Amaël Broustet , Andreas Höring

In this note we collect some results on the deformation theory of toric Fano varieties.

Algebraic Geometry · Mathematics 2022-06-22 Andrea Petracci

We prove divisorial canonicity of Fano hypersurfaces and double spaces of general position with elementary singularities.

Algebraic Geometry · Mathematics 2008-07-25 Aleksandr Pukhlikov

Let X be a Fano variety of dimension n, pseudoindex i_X and Picard number \rho_X. A generalization of a conjecture of Mukai says that \rho_X(i_X-1)\le n. We prove that the conjecture holds if: a) X has pseudoindex i_X \ge \frac{n+3}{3} and…

Algebraic Geometry · Mathematics 2007-05-23 Marco Andreatta , Elena Chierici , Gianluca Occhetta

Mukai varieties are Fano varieties of Picard number one and coindex three. In genus seven to ten they are linear sections of some special homogeneous varieties. We describe the generic automorphism groups of these varieties. When they are…

Algebraic Geometry · Mathematics 2022-02-01 Thomas Dedieu , Laurent Manivel