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We prove the Integral Hodge Conjecture for curve classes on smooth varieties of dimension at least three with nef anticanonical divisor constructed as a complete intersection of ample hypersurfaces in a smooth toric variety. In particular,…

Algebraic Geometry · Mathematics 2022-10-07 Bjørn Skauli

We get sharp degree bound for generic smoothness and connectedness of the space of conics in low degree complete intersections which generalizes the old work about Fano scheme of lines on Hypersurfaces.

Algebraic Geometry · Mathematics 2013-07-25 Hong R. Zong

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

We describe a class of affine toric varieties $V$ that are set-theoretically minimally defined by codim $V+1$ binomial equations over fields of any characteristic.

Algebraic Geometry · Mathematics 2007-05-23 Margherita Barile

For a smooth curve $B$ over an algebraically closed field $k$, for every $B$-flat complete intersection $X_B$ in $B\times_{\text{Spec}\ k} \mathbb{P}^n_k$ of type $(d_1,\dots,d_c)$, if the Fano index is $\geq 2$ and if…

Algebraic Geometry · Mathematics 2018-12-31 Jason Michael Starr , Zhiyu Tian , Runhong Zong

We show that the usual sufficient criterion for a generic hypersurface in a smooth projective manifold to have the same Picard number as the ambient variety can be generalized to hypersurfaces in complete simplicial toric varieties. This…

Algebraic Geometry · Mathematics 2013-05-29 Ugo Bruzzo , Antonella Grassi

We prove two conjectures on weighted complete intersections and give the complete classification of threefold weighted complete intersections in weighted projective space that are canonically or anticanonically embedded.

Algebraic Geometry · Mathematics 2012-01-04 Jheng-Jie Chen , Jungkai Alfred Chen , Meng Chen

We obtain criteria for detecting complete intersections in projective varieties. Motivated by a conjecture of Hartshorne concerning subvarieties of projective spaces, we investigate situations when two-codimensional smooth subvarieties of…

Algebraic Geometry · Mathematics 2020-12-01 Mihai Halic

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 study smooth toric Fano varieties using primitive relations and toric Mori theory. We show that for any irreducible invariant divisor D in a toric Fano variety X, we have $0\leq\rho_X-\rho_D\leq 3$, for the difference of…

Algebraic Geometry · Mathematics 2007-05-23 Cinzia Casagrande

In this paper we prove that any smooth prime Fano threefold, different from the Mukai-Umemura threefold, contains a 1-dimensional family of intersecting lines. Combined with a result of the second author (see J. Algebr. Geom. 8:2 (1999),…

Algebraic Geometry · Mathematics 2007-05-23 Atanas Iliev , Carmen Schuhmann

We study genus 1 Gromov-Witten invariants of Fano complete intersections in the projective spaces. Among other things, we show a reconstruction theorem for genus 1 invariants with only ambient insertions, and compute the genus 1 invariants…

Algebraic Geometry · Mathematics 2022-03-16 Xiaowen Hu

We give lower bounds for Hodge numbers of smooth well formed Fano weighted complete intersections. In particular, we compute their Hodge level, that is, the maximal distance between non-trivial Hodge numbers in the same row of the Hodge…

Algebraic Geometry · Mathematics 2020-08-13 Victor Przyjalkowski , Constantin Shramov

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

For any $n\geq 3$, we explicitly construct smooth projective toric $n$-folds of Picard number $\geq 5$, where any nontrivial nef line bundles are big.

Algebraic Geometry · Mathematics 2008-10-24 Osamu Fujino , Hiroshi Sato

A horospherical variety is a normal algebraic variety where a reductive algebraic group acts with an open orbit which is a torus bundle over a flag variety. For example, toric varieties and flag varieties are horospherical. In this paper,…

Algebraic Geometry · Mathematics 2007-05-23 Boris Pasquier

Let $X$ be a complex smooth Fano variety of dimension $n$. In this paper, we give a classification of such $X$ when the pseudoindex is equal to $\dfrac{\dim X+1}{2}$ and the Picard number greater than one.

Algebraic Geometry · Mathematics 2024-09-23 Kiwamu Watanabe

We prove the following: (a) Let X be a smooth, codimension two subvariety of P6. If X lies on a hyperquintic or if deg(X)<74, then X is a complete intersection. (b) Let X be a smooth, subcanonical threefold in P5. If X lies on a…

Algebraic Geometry · Mathematics 2007-05-23 Philippe Ellia , Davide Franco

In this work we provide effective bounds and classification results for rational $\QQ$-factorial Fano varieties with a complexity-one torus action and Picard number one depending on the invariants dimension and Picard index. This…

Algebraic Geometry · Mathematics 2012-11-26 Elaine Herppich

This paper is devoted to the study of holomorphic distributions of dimension and codimension one on smooth weighted projective complete intersection Fano manifolds threedimensional, with Picard number equal to one. We study the relations…

Algebraic Geometry · Mathematics 2020-01-31 Alana Cavalcante , Mauricio Corrêa , Simone Marchesi