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We prove that every smooth Fano complete intersection of index $1$ and codimension $r$ in $\mathbb{P}^{n+r}$ is birationally superrigid and K-stable if $n\ge 10r$. We also propose a generalization of Tian's criterion of K-stability and, as…

Algebraic Geometry · Mathematics 2021-02-22 Ziquan Zhuang

We show that every reductive subgroup of the automorphism group of a quasi-smooth well formed weighted complete intersection is a restriction of a subgroup in the automorphism group in the ambient weighted projective space. Also, we provide…

Algebraic Geometry · Mathematics 2023-02-08 Victor Przyjalkowski , Constantin Shramov

Small codimensional embedded manifolds defined by equations of small degree are Fano and covered by lines. They are complete intersections exactly when the variety of lines through a general point is so and has the right codimension. This…

Algebraic Geometry · Mathematics 2012-09-11 Paltin Ionescu , Francesco Russo

In this paper we compute the cohomology of the Fano varieties of $k$-planes in the smooth complete intersection of two quadrics in $\mathbb{P}^{2g+1}$, using Springer theory for symmetric spaces.

Algebraic Geometry · Mathematics 2020-06-23 Tsao-Hsien Chen , Kari Vilonen , Ting Xue

We prove that a generic (in the sense of Zariski topology) Fano complete intersection $V$ of the type $(d_1,...,d_k)$ in ${\mathbb P}^{M+k}$, where $d_1+...+d_k=M+k$, is birationally superrigid if $M\geq 7$, $M\geq k+3$ and $\mathop{\rm…

Algebraic Geometry · Mathematics 2011-10-11 Aleksandr Pukhlikov

Given a hypersurface $i \colon X \hookrightarrow \widetilde{P}^n$ in a weighted projective space, we compute the intersection form on the second cohomology $H^2(X, \mathbb{Z})^{\otimes n-1} \to \mathbb{Z}$ for the purpose of identifying…

Algebraic Geometry · Mathematics 2025-06-05 Anna-Maria Raukh

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

Algebraic Geometry · Mathematics 2008-07-25 Aleksandr Pukhlikov

In this short note, we study the semi-simplicity of the quantum cohomology algebra H(V, C) of a Fano complete intersection V, and show that the subspace of H(V, C) generated by the hyperplane sections is semi-simple in the sense of Dubrovin…

alg-geom · Mathematics 2008-02-03 Gang Tian , Geng Xu

We show that being a general fibre of a Mori fibre space is a rather restrictive condition for a Fano variety. More specifically, we obtain two criteria (one sufficient and one necessary) for a Q-factorial Fano variety with terminal…

Algebraic Geometry · Mathematics 2016-06-09 Giulio Codogni , Andrea Fanelli , Roberto Svaldi , Luca Tasin

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

The goal of this article is to study the equations and syzygies of embeddings of rational surfaces and certain Fano varieties. Given a rational surface X and an ample and base-point-free line bundle L on X, we give an optimal numerical…

Algebraic Geometry · Mathematics 2007-05-23 Francisco Javier Gallego , B. P. Purnaprajna

Let $X\subset P^n$ be a complex projective manifold of degree $d$ and arbitrary dimension. The main result of this paper gives a classification of such manifolds (assumed moreover to be connected, non-degenerate and linearly normal) in case…

Algebraic Geometry · Mathematics 2007-05-23 Paltin Ionescu

We show that complex Fano hypersurfaces can have arbitrarily large degrees of irrationality. More precisely, if we fix a Fano index e, then the degree of irrationality of a very general complex Fano hypersurface of index e and dimension n…

Algebraic Geometry · Mathematics 2021-11-11 Nathan Chen , David Stapleton

It is proved that the global log canonical threshold of a Zariski general Fano complete intersection of index 1 and codimension $k$ in ${\mathbb P}^{M+k}$ is equal to one, if $M\geqslant 2k+3$ and the maximum of the degrees of defining…

Algebraic Geometry · Mathematics 2017-04-04 Aleksandr V. Pukhlikov

Any smooth projective variety contains many complete intersection subvarieties with ample cotangent bundles, of each dimension up to half its own dimension.

Algebraic Geometry · Mathematics 2017-12-11 Damian Brotbek , Lionel Darondeau

For a smooth complete intersection X, we consider a general fiber \mathbb{F} of the evaluation map ev of Kontsevich moduli space \bar{M}_{0,m}(X,m)\rightarrow X^m and the forgetful functor F : \mathbb{F} \rightarrow \bar{M}_{0,m}. We prove…

Algebraic Geometry · Mathematics 2017-01-17 Xuanyu Pan

We survey what is known about Fano threefold weighted complete intersections from the point of view of birational rigidity.

Algebraic Geometry · Mathematics 2025-08-20 Tiago Duarte Guerreiro , Takuzo Okada

A nef-partition for a weighted complete intersection is a combinatorial structure on its weights and degrees which is important for Mirror Symmetry. It is known that nef-partitions exist for smooth well-formed Fano weighted complete…

Algebraic Geometry · Mathematics 2023-12-13 Mikhail Ovcharenko

In this paper we examine different problems regarding complete intersection varieties of high degree in a complex projective space. First we show how one can deduce hyperbolicity for generic complete intersection of high multidegree and…

Algebraic Geometry · Mathematics 2019-02-20 Damian Brotbek

We compute the quantum Euler class of Fano complete intersections X in a projective space. In particular, we prove a recent conjecture of A. Buch and R. Pandharipande. Finally we apply our result to obtain formulas for the virtual Tevelev…

Algebraic Geometry · Mathematics 2022-04-05 Alessio Cela