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We prove that a family of varieties is birationally isotrivial if all the fibers are birational to each other.

Algebraic Geometry · Mathematics 2017-09-18 Fedor Bogomolov , Christian Böhning , Hans-Christian Graf von Bothmer

Cylinders in Fano varieties receives a lot of attentions recently from the viewpoints of birational geometry and unipotent geometry. In this article, we provide a survey of several known et new results concerning the anti-canonically polar…

Algebraic Geometry · Mathematics 2026-03-13 Adrien Dubouloz , In-Kyun Kim , Takashi Kishimoto , Joonyeong Won

We determine birational superrigidity for a quasi-smooth prime Fano 3-fold of codimension 4 with no projection centers. In particular we prove birational superrigidity for Fano 3-folds of codimension 4 with no projection centers which are…

Algebraic Geometry · Mathematics 2020-03-18 Takuzo Okada

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 give several examples of pairs of non-isomorphic cubic fourfolds whose Fano varieties of lines are birationally equivalent (and in one example isomorphic). Two of our examples, which are special families of conjecturally irrational…

Algebraic Geometry · Mathematics 2024-12-20 Corey Brooke , Sarah Frei , Lisa Marquand

In this paper we consider Q-Fano 3-fold weighted complete intersections of codimension 2 in the 85 families listed in the Iano-Fletcher's list and determine which cycle is a maximal center or not. For each maximal center, we construct…

Algebraic Geometry · Mathematics 2014-02-06 Takuzo Okada

Sextic double solids, double covers of $\mathbb P^3$ branched along a sextic surface, are the lowest degree Gorenstein Fano 3-folds, hence are expected to behave very rigidly in terms of birational geometry. Smooth sextic double solids, and…

Algebraic Geometry · Mathematics 2024-12-25 Erik Paemurru

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

Algebraic Geometry · Mathematics 2008-07-25 Aleksandr Pukhlikov

We prove that every birationally superrigid Fano variety whose alpha invariant is greater than (resp. no smaller than) $\frac{1}{2}$ is K-stable (resp. K-semistable). We also prove that the alpha invariant of a birationally superrigid Fano…

Algebraic Geometry · Mathematics 2019-08-15 Charlie Stibitz , Ziquan Zhuang

We propose a new method to study birational maps between Fano varieties based on multiplier ideal sheaves. Using this method, we prove equivariant birational rigidity of four Fano threefolds acted on by the group A6. As an application, we…

Algebraic Geometry · Mathematics 2011-12-08 Ivan Cheltsov , Constantin Shramov

In this short note we prove that in many cases the failure of a variety to be separably rationally connected is caused by the instability of the tangent sheaf (if there are no other obvious reasons). A simple application of the results…

Algebraic Geometry · Mathematics 2014-07-30 Zhiyu Tian

We prove that the Fano variety of lines of a generic cubic fourfold containing a plane is isomorphic to a moduli space of twisted stable complexes on a K3 surface. On the other hand, we show that the Fano varieties are always birational to…

Algebraic Geometry · Mathematics 2011-12-26 Emanuele Macri , Paolo Stellari

We prove results about 1-cycles on certain Fano varieties using techniques that rely on rational curves. Firstly, we show that Fano weighted complete intersections with index bigger than half their dimension have trivial first Griffiths…

Algebraic Geometry · Mathematics 2017-11-29 Cristian Minoccheri , Xuanyu Pan

We show that any quasismooth Fano threefold weighted complete intersections of type $(12, 14)$ in $\mathbb{P} (1, 2, 3, 4, 7, 11)$ is birationally solid.

Algebraic Geometry · Mathematics 2025-11-10 Takuzo Okada

In this paper we prove that a regular foliation on a complex weak Fano manifold is algebraically integrable.

Algebraic Geometry · Mathematics 2015-10-19 Stéphane Druel

In this note, we reduce various conjectures in birational geometry, including Shokurov conjecture on singularities of the base of log Calabi-Yau fibrations of Fano type and boundedness conjecture for rationally connected Calabi-Yau…

Algebraic Geometry · Mathematics 2026-03-16 Guodu Chen , Chuyu Zhou

We prove divisorial canonicity of Fano double hypersurfaces of general position.

Algebraic Geometry · Mathematics 2009-11-13 Aleksandr Pukhlikov

We prove the birational superrigidity and the nonrationality of a cyclic triple cover of $\mathbb{P}^{2n}$ branched over a nodal hypersurface of degree $3n$ for $n\ge 2$. In particular, the obtained result solves the problem of the…

Algebraic Geometry · Mathematics 2015-06-26 Ivan Cheltsov

We study a particular kind of fiber type contractions between complex, projective, smooth varieties f:X->Y, called Fano conic bundles. This means that X is a Fano variety, and every fiber of f is isomorphic to a plane conic. Denoting by…

Algebraic Geometry · Mathematics 2018-03-15 Eleonora Anna Romano

We find a relation between a cubic hypersurface $Y$ and its Fano variety of lines $F(Y)$ in the Grothendieck ring of varieties. We prove that if the class of an affine line is not a zero-divisor in the Grothendieck ring of varieties, then…

Algebraic Geometry · Mathematics 2014-06-27 Sergey Galkin , Evgeny Shinder