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Iterating the procedure of making a double cover over a given variety, we construct large families of smooth higher-dimensional Fano varieties of index 1. These varieties can be realized as complete intersections in various weighted…

Algebraic Geometry · Mathematics 2015-06-26 Aleksandr V. Pukhlikov

It is proved that a general Fano hypersurface of index 1 (in the projective space) with isolated singularities of general position is birationally rigid. Therefore it cannot be fibered into uniruled varieties of a smaller dimension by a…

Algebraic Geometry · Mathematics 2015-06-26 Aleksandr V. Pukhlikov

We classify birationally rigid orbifold Fano 3-folds of index one defined by $5 \times 5$ Pfaffians. We give a sharp criterion for birational rigidity of these families based on the type of singularities that the varieties admit. Various…

Algebraic Geometry · Mathematics 2022-07-22 Hamid Abban , Takuzo Okada

We complete the study of birational geometry of Fano fiber spaces $\pi\colon V\to {\mathbb P}^1$, the fiber of which is a Fano double hypersurface of index 1. For each family of these varieties we either prove birational rigidity or produce…

Algebraic Geometry · Mathematics 2015-06-26 Aleksandr V. Pukhlikov

We give conditions for a uniruled variety of dimension at least 2 to be non-solid. This study provides further evidence to a conjecture by Abban and Okada on the solidity of Fano 3-folds. To complement our results we write explicit…

Algebraic Geometry · Mathematics 2023-07-07 Livia Campo , Tiago Duarte Guerreiro

We continue to study birational geometry of Fano fibrations $\pi\colon V\to {\mathbb P}^1$ the fibers of which are Fano double hypersurfaces of index 1. For a majority of families of this type, which do not satisfy the condition of…

Algebraic Geometry · Mathematics 2015-06-26 A. V. Pukhlikov

A Fano variety of Picard number $1$ is said to be \textit{birationally solid} if it is not birational to a Mori fiber space over a positive dimensional base. In this paper we complete the classification of quasi-smooth birationally solid…

Algebraic Geometry · Mathematics 2023-09-12 Takuzo Okada

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

In this paper we prove birational rigidity of large classes of Fano-Mori fibre spaces over a base of arbitrary dimension, bounded from above by a constant that depends on the dimension of the fibre only. In order to do that, we first show…

Algebraic Geometry · Mathematics 2015-09-30 Aleksandr V. Pukhlikov

We consider slope stability of the canonical extension of the tangent bundle by the trivial line bundle and with the extension class c_1(T_X) on Picard-rank-1 Fano varieties. In cases where the index divides the dimension or the dimension…

Algebraic Geometry · Mathematics 2023-05-02 Kuang-Yu Wu

For $n\geq 4$, let $X$ be a complex smooth Fano $n$-fold whose minimal anticanonical degree of non-free rational curves on $X$ is at least $n-2$. We classify extremal contractions of such varieties. As an application, we obtain a…

Algebraic Geometry · Mathematics 2024-06-04 Kiwamu Watanabe

We prove that a quasi-smooth Fano threefold hypersurface is birationally rigid if and only if it has Fano index one.

Algebraic Geometry · Mathematics 2020-07-29 Hamid Ahmadinezhad , Ivan Cheltsov , Jihun Park

We prove birational superrigidity of Fano double hypersurfaces of index one with quadratic and multi-quadratic singularities, satisfying certain regularity conditions, and give an effective explicit lower bound for the codimension of the…

Algebraic Geometry · Mathematics 2018-12-31 Thomas Eckl , Aleksandr Pukhlikov

We prove that a general Fano fibration $\pi\colon V\to {\mathbb P}^1$, the fiber of which is a double Fano hypersurface of index 1, is birationally superrigid provided it is sufficiently twisted over the base. In particular, on $V$ there…

Algebraic Geometry · Mathematics 2007-05-23 Aleksandr V. Pukhlikov

We prove that a smooth Fano hypersurface $V=V_M\subset{\Bbb P}^M$, $M\geq 6$, is birationally superrigid. In particular, it cannot be fibered into uniruled varieties by a non-trivial rational map and each birational map onto a minimal Fano…

Algebraic Geometry · Mathematics 2015-06-26 Aleksandr V. Pukhlikov

We describe the set of Mori structures for a Fano 3-fold of index 2 and degree 1 (the double cone over the Veronese surface). In partiular, it is proved that such a Fano variety is not rational, the group of birational automorphisms…

Algebraic Geometry · Mathematics 2007-05-23 Mikhail Grinenko

Determining when the birational automorphism group of a Fano variety is finite is an interesting and difficult problem. The main technique for studying this problem is by the Noether-Fano method. This method has been effective in studying…

Algebraic Geometry · Mathematics 2022-05-20 David Stapleton , Nathan Chen

We give a brief survey of the concept of birational rigidity, from its origins in the two-dimensional birational geometry, to its current state. The main ingredients of the method of maximal singularities are discussed. The principal…

Algebraic Geometry · Mathematics 2007-05-23 Aleksandr V. Pukhlikov

In this paper, we give some results on the birational geometry of varieties of Fano type and boundedness problems in positive characteristic, including a result ensuring that boundedness is invariant under normalizations, a canonical bundle…

Algebraic Geometry · Mathematics 2025-03-10 Xintong Jiang

In this paper a large class of Fano double quadrics and cubics are shown to be factorial and birationally superrigid, in particular they admit no non-trivial structure of a fibration with rationally connected fibres and are therefore…

Algebraic Geometry · Mathematics 2018-01-30 Ewan Johnstone
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