A remark on algebraic cycles on cubic fourfolds

Abelian automorphism groups of cubic fourfolds

We list all finite abelian groups which act effectively on smooth cubic fourfolds.

Voevodsky's conjecture for cubic fourfolds and Gushel-Mukai fourfolds via noncommutative K3 surfaces

In the first part of this paper we will prove the Voevodsky's nilpotence conjecture for smooth cubic fourfolds and ordinary generic Gushel-Mukai fourfolds. Then, making use of noncommutative motives, we will prove the Voevodsky's nilpotence conjecture for generic Gushel-Mukai fourfolds containing a $τ$-plane $\G(2,3)$ and for ordinary Gushel-Mukai fourfolds containing a quintic del Pezzo surface.

On cubic fourfolds with an inductive structure

We study the number of planes for four dimensional projective hypersurfaces which has so-called inductive structure. We also determine transcendental lattices for cubic fourfolds of this type.

Derived categories of cubic fourfolds

We discuss the structure of the derived category of coherent sheaves on cubic fourfolds of three types: Pfaffian cubics, cubics containing a plane and singular cubics, and discuss its relation to the rationality of these cubics.

The moduli space of cubic fourfolds

We describe the GIT compactification of the moduli space of cubic fourfolds, with a special emphasis on the role played by singularities. Our main result is that a cubic fourfold with only isolated simple (A-D-E) singularities is GIT stable. Conversely, with some minor exceptions, the stability for cubic fourfolds is characterized by this condition.

On lattice polarizable cubic fourfolds

We extend non-emtpyness and irreducibility of Hassett divisors to the moduli spaces of $M$-polarizable cubic fourfolds for higher rank lattices $M$, which in turn provides a systematic approach for describing the irreducible components of intersection of Hassett divisors. We show that Fermat cubic fourfold is contained in every Hassett divisor, which yields a new proof of Hassett's existence theorem of special cubic fourfolds. We obtain an algorithm to determine the irreducible components of the intersection of any two Hassett divisors and we give new examples of rational cubic fourfolds. More…

Classification of polarized symplectic automorphisms of Fano varieties of cubic fourfolds

We classify the polarized symplectic automorphisms of Fano varieties of smooth cubic fourfolds (equipped with the Plücker polarization) and study the fixed loci.

Automorphisms and Periods of Cubic Fourfolds

We classify the symplectic automorphism groups for cubic fourfolds. The main inputs are the global Torelli theorem for cubic fourfolds and the classification of the fixed-point sublattices of the Leech lattice. Among the highlights of our results, we note that there are 34 possible groups of symplectic automorphisms, with 6 maximal cases. The six maximal cases correspond to 8 non-isomorphic, and isolated in moduli, cubic fourfolds; six of them previously identified by other authors. Finally, the Fermat cubic fourfold has the largest possible order (174,960) for the automorphism group (non-nece…

Hilbert schemes of two points on K3 surfaces and certain rational cubic fourfolds

In this paper, we check that Fano schemes of lines on certain rational cubic fourfolds are birational to Hilbert schemes of two points on K3 surfaces.

Lagrangian embeddings of cubic fourfolds containing a plane

We prove that a very general cubic fourfold containing a plane can be embedded into a holomorphic symplectic eightfold as a Lagrangian submanifold. We construct the desired holomorphic symplectic eightfold as a moduli space of Bridgeland stable objects in the derived category of the twisted K3 surface corresponding to the cubic fourfold containing a plane.

A remark on the Torelli theorem for cubic fourfolds

In this note, we give a short proof of the Torelli theorem for cubic fourfolds that relies on the global Torelli theorem for irreducible holomorphic symplectic varieties proved by Verbitsky.

A family of cubic fourfolds with finite-dimensional motive

We prove that cubic fourfolds in a certain 10-dimensional family have finite-dimensional motive. The proof is based on the van Geemen-Izadi construction of an algebraic Kuga-Satake correspondence for these cubic fourfolds, combined with Voisin's method of "spread". Some consequences are given.

Twisted cubics on singular cubic fourfolds - On Starr's fibration

We study lines and twisted cubics on cubic fourfolds with simple isolated singularities. We show that the Hilbert scheme compactification of the total space of Starr's fibration on the space of twisted cubics on a cubic fourfold with simple isolated singularities and not containing a plane admits a contraction to a singular projective symplectic variety of dimension eight. The latter admits a crepant resolution which is a deformation of the symplectic eightfold constructed from the space of twisted cubics on a smooth cubic fourfold. Thereby we give another proof of the fact that the latter is …

判别式24的三次四重簇与有理性质

Cubic fourfolds of discriminant 24 and rationality

本文研究判别式24的三次四重簇，通过其扭曲曲面中Brauer类消失的条件，证明了有理性质，并构造了可数无穷多个新的有理例子。

Ulrich bundles on cubic fourfolds

We show the existence of rank 6 Ulrich bundles on a smooth cubic fourfold. First, we construct a simple sheaf E of rank 6 as an elementary modification of an ACM bundle of rank 6 on a smooth cubic fourfold. Such an E appears as an extension of two Lehn-Lehn-Sorger-van Straten sheaves. Then we prove that a general deformation of E(1) becomes Ulrich. In particular, this says that general cubic fourfolds have Ulrich complexity 6.

具有素数阶辛自同构的立方四维流形

Cubic fourfolds with a symplectic automorphism of prime order

本文研究了具有素数阶辛自同构的立方四维流形，证明其为理性的条件，并展示了两个非等变理性的有理立方四维流形家族。

含高度奇异超平面截面的立方四重面

Cubic fourfolds containing highly singular hyperplane sections

本研究构造了五个不可约除子，用于参数化含高度奇异超平面截面的光滑立方四重面，并证明这些除子不是Noether-Lefschetz除子。

Maximally Algebraic potentially irrational Cubic Fourfolds

A well known conjecture asserts that a cubic fourfold $X$ whose transcendental cohomology $T_X$ can not be realized as the transcendental cohomology of a $K3$ surface is irrational. Since the geometry of cubic fourfolds is intricately related to the existence of algebraic $2$-cycles on them, it is natural to ask for the most algebraic cubic fourfolds $X$ to which this conjecture is still applicable. In this paper, we show that for an appropriate `algebraicity index' $κ_X$, there exists a unique class of cubics maximizing $κ_X$, not having an associated $K3$ surface; namely, the cubic fourfolds…

一般的Hassett极大立方四维流形的方程

The equations of general Hassett maximal cubic fourfolds

本文研究Hassett极大立方四维流形，构造了最大维数为十六的locus的不可约分量，并利用代数和算术方法分析相关晶格。

关于立方四重曲面无理性的研究

On the irrationality of cubic fourfolds

该研究证明了立方四重曲面的原始上同调群与K3曲面的中间上同调群同构，揭示了其无理性特征。

Cubic Fourfolds with an Involution

There are three types of involutions on a cubic fourfold; two of anti-symplectic type, and one symplectic. Here we show that cubics with involutions exhibit the full range of behaviour in relation to rationality conjectures. Namely, we show a general cubic fourfold with symplectic involution has no associated K3 surface and is conjecturely irrational. In contrast, we show a cubic fourfold with a particular anti-symplectic involution has an associated K3, and is in fact rational. We show such a cubic is contained in the intersection of all non-empty Hassett divisors; we call such a cubic Hasset…

非常一般特殊三次四维流形的K3范畴的Fourier-Mukai数

Fourier-Mukai numbers of K3 categories of very general special cubic fourfolds

本文针对非常一般特殊三次四维流形，研究其K3范畴的Fourier-Mukai伙伴数量，并给出了相应的计数公式。

A family of special cubic fourfolds with motive of abelian type

In this short note, we show that there exist one dimensional families of cubic fourfolds with Chow motive of abelian type and finite dimensional inside every Hassett divisor of special cubic fourfolds. This also implies abelianity and finite dimensionality of the motive of related Hyperkähler varieties, such as the Fano variety of lines and the LLSvS 8fold.

Cubic fourfolds, K3 surfaces, and rationality questions

This is a survey of the geometry of complex cubic fourfolds with a view toward rationality questions. Topics include classical constructions of rational examples, Hodge structures and special cubic fourfolds, associated K3 surfaces and their geometric interpretations, and connections with rationality and unirationality constructions.

Flops on holomorphic symplectic fourfolds and determinantal cubic hypersurfaces

We study the birational geometry of irreducible holomorphic symplectic varieties arising as varieties of lines of general cubic fourfolds containing a cubic scroll. We compute the ample and moving cones, and exhibit a birational automorphism of infinite order explaining the chamber decomposition of the moving cone.

The moduli space of cubic fourfolds via the period map

We characterize the image of the period map for cubic fourfolds with at worst simple singularities as the complement of an arrangement of hyperplanes in the period space. It follows then that the GIT compactification of the moduli space of cubic fourfolds is isomorphic to the Looijenga's compactification associated to this arrangement. This work builds on and is a natural continuation of our previous paper on the GIT compactification of the moduli space of cubic fourfolds.

具有辛自同构的立方四维流形

Cubic fourfolds with symplectic automorphisms

本文通过分类特定群的表示，确定具有辛自同构的立方四维流形的射影方程及模空间的不可约分量数量，并探讨了其定义域。

由Cremona变换产生的新有理三次四维流形

New rational cubic fourfolds arising from Cremona transformations

本文证明判别式20的非常一般三次四维流形中Fourier-Mukai等价蕴含双有理等价，并借助Veronese曲面定义的Cremona变换发现新的有理三次四维流形。

三次四维流形的等变双有理几何与导出范畴

Equivariant birational geometry of cubic fourfolds and derived categories

本文从导出范畴角度研究等变双有理性，构造了有限群在光滑三次四维流形上非线性化但稳定线性化的作用实例。

Algebraic cycles and very special cubic fourfolds

Informed by the Bloch-Beilinson conjectures, Voisin has made a conjecture about $0$-cycles on self-products of Calabi-Yau varieties. In this note, we consider variant versions of Voisin's conjecture for cubic fourfolds, and for hyperkähler varieties. We present examples for which these conjectures are verified, by considering certain very special cubic fourfolds and their Fano varieties of lines.

Universal unramified cohomology of cubic fourfolds containing a plane

We prove the universal triviality of the third unramified cohomology group of a very general complex cubic fourfold containing a plane. The proof uses results on the unramified cohomology of quadrics due to Kahn, Rost, and Sujatha.

A remark on the non-rationality Problem for generic cubic fourfolds

It is proved that the non-rationality of a generic cubic fourfold follows from a conjecture on the non-decomposability in the direct sum of non-trivial polarized Hodge structures of the polarized Hodge structure on transcendental cycles on a projective surface.

The derived category of a non generic cubic fourfold containing a plane

We describe an Azumaya algebra on the resolution of singularities of the double cover of a plane ramified along a nodal sextic associated to a non generic cubic fourfold containing a plane. We show that the derived category of such a resolution, twisted by the Azumaya algebra, is equivalent to the Kuznetsov component in the semiorthogonal decomposition of the derived category of the cubic fourfold.

Modular Forms and Special Cubic Fourfolds

We study the degree of the special cubic fourfolds in the Hilbert scheme of cubic fourfolds via a computation of the generating series of Heegner divisors of even lattice of signature (2, 20).

Stable Ulrich bundles on cubic fourfolds

In this paper, we give necessary and sufficient conditions for the existence of Ulrich bundles on cubic fourfold $X$ of given rank $r$. As consequences, we show that for every integer $r\ge 2$ there exists a family of indecomposable rank $r$ Ulrich bundles on the certain cubic fourfolds, depending roughly on $r$ parameters, and in particular they are of wild representation type; special surfaces on the cubic fourfolds are explicitly constructed by Macaulay2; a new $19$-dimensional family of projective ten-dimensional irreducible holomorphic symplectic manifolds associated to a certain cubic fo…

L等价与三次四维流形的傅里叶-穆卡伙伴

L-equivalence and Fourier--Mukai partners of cubic fourfolds

本文研究了三次四维流形的L等价与傅里叶-穆卡伙伴，通过衍生Torelli型准则和判别式条件，证明了计数公式并展示了有限的L等价类。

Abelian Automorphism Groups of Quartic Surfaces and Cubic Fourfolds

In this paper, we develop a new method to classify abelian automorphism groups of hypersurfaces. We use this method to classify (Theorem 4.2) abelian groups that admit a liftable action on a smooth cubic fourfold. A parallel result (Theorem 5.1) is obtained for quartic surfaces.

Moduli spaces of twisted K3 surfaces and cubic fourfolds

Motivated by the relation between (twisted) K3 surfaces and special cubic fourfolds, we construct moduli spaces of polarized twisted K3 surfaces of any fixed degree and order. We do this by mimicking the construction of the moduli space of untwisted polarized K3 surfaces as a quotient of a bounded symmetric domain.

Cubic fourfolds containing a plane and K3 surfaces of Picard rank two

We present some families of cubic hypersurfaces in $\mathbb P^5 (\mathbb C)$ containing a plane whose associated quadric bundle does not have a rational section.

Variety of power sums and divisors in the moduli space of cubic fourfolds

We show that a cubic fourfold F that is apolar to a Veronese surface has the property that its variety of power sums VSP(F,10) is singular along a K3 surface of genus 20. We prove that these cubics form a divisor in the moduli space of cubic fourfolds and that this divisor is not a Noether-Lefschetz divisor. We use this result to prove that there is no nontrivial Hodge correspondence between a very general cubic and its VSP.

含平面的三次三维簇与四维簇上的直线

Lines on cubic threefolds and fourfolds containing a plane

该研究刻画了特征非2域上含平面的一般三次三维簇的直线Fano概形，以此刻画非闭域上这类三次三维簇的有理性，并显式构造含平面三次四维簇直线Fano簇的拉格朗日纤维化。

Fourier-Mukai partners for very general special cubic fourfolds

We exhibit explicit examples of very general special cubic fourfolds with discriminant $d$ admitting an associated (twisted) K3 surface, which have non-isomorphic Fourier-Mukai partners. In particular, in the untwisted setting, we show that the number of Fourier-Mukai partners for a very general special cubic fourfold with discriminant $d$ and having an associated K3 surface, is equal to the number $m$ of Fourier-Mukai partners of its associated K3 surface, if $d \equiv 2 (\text{mod}\,6)$; else, if $d \equiv 0 (\text{mod}\,6)$, the cubic fourfold has $\lceil m/2 \rceil$ Fourier-Mukai partners.

与极好三次四重相关联的相对紧化Prym与Picard纤维化

Relative compactified Prym and Picard fibrations associated to very good cubic fourfolds

本文证明极好三次四重对应的相对紧化Prym与Picard纤维化的规范化是光滑的，推广了Laza、Saccà和Voisin的结果。

奇异循环三次四重簇上直线的Fano簇

The Fano variety of lines on singular cyclic cubic fourfolds

本文研究奇异循环三次四重簇上直线Fano簇的辛解消，特别关注沿具有$A_i$型孤立奇点的三次三重簇分支的情形，并发现覆盖自同构诱导的三阶非辛自同构。

Brill-Noether special cubic fourfolds of discriminant 14

We study the Brill-Noether theory of curves on K3 surfaces that are Hodge theoretically associated to cubic fourfolds of discriminant 14. We prove that any smooth curve in the polarization class has maximal Clifford index and deduce that a cubic fourfold contains disjoint planes if and only if it admits a Brill-Noether special associated K3 surface of degree 14. As an application, the complement of the pfaffian locus, inside the Noether-Lefschetz divisor of discriminant 14 in the moduli space of cubic fourfolds, is contained in the irreducible locus of cubic fourfolds containing two disjoint p…

三次四折体中的平面

Planes in cubic fourfolds

该研究确定了复光滑三次四折体中平面的最大数量为405（仅费马三次四折体可达）、实光滑三次四折体中实平面的最大数量为357（由Clebsch–Segre三次四折体实现），且射影等价下平面数超350的三次四折体仅有三类。

Twisted cubics on cubic fourfolds

We construct a new twenty-dimensional family of projective eight-dimensional irreducible holomorphic symplectic manifolds: the compactified moduli space M_3(Y) of twisted cubics on a smooth cubic fourfold Y that does not contain a plane is shown to be smooth and to admit a contraction M_3(Y) -> Z(Y) to a projective eight-dimensional symplectic manifold Z(Y). The construction is based on results on linear determinantal representations of singular cubic surfaces.

Nonrationality of a generic cubic fourfold

An error in Section 4 invalidates all the main results of the paper.

O'Grady 十维流形与三次四维流形的素数阶非辛自同构

Non-symplectic automorphisms of prime order of O'Grady's tenfolds and cubic fourfolds

本文分类 OG10 型不可约全纯辛流形的素数阶非辛自同构，刻画其由三次四维流形诱导的情形，并用于探讨相关有理性猜想。

关于三次四维流形和超Kähler流形的L等价的一些注记

Some remarks on L-equivalence for cubic fourfolds and hyper-Kähler manifolds

本文证明了非常一般的三次四维流形在L等价时必为同构，同时指出存在特殊三次四维流形在L等价但非同构。当三次四维流形在特定Hassett除子中非常一般时，L等价的流形也是傅里叶-莫克伴侣。此外，作者还提供了进一步的例子支持L等价的超Kähler流形应为D等价的猜想。

关于包含多个平面的四次三维簇的一个注记

A note on cubic fourfolds containing several planes

研究包含多个平面（特别是沿直线相交的两个平面）的四次三维簇的几何、Hodge理论和导出范畴，并关联到扭曲K3曲面。

Potential density of rational points on the variety of lines of a cubic fourfold

We prove the potential density of rational points on the variety of lines of a sufficiently general cubic fourfold defined over a number field, where ``sufficiently general'' means that a condition of Terasoma type is satisfied. These varieties have trivial canonical bundle and have geometric Picard group equal to $\mathbb{Z}$.

Some non-special cubic fourfolds

In [1309.1899], Ranestad and Voisin showed, quite surprisingly, that the divisor in the moduli space of cubic fourfolds consisting of cubics "apolar to a Veronese surface" is not a Noether-Lefschetz divisor. We give an independent proof of this by exhibiting an explicit cubic fourfold X in the divisor and using point counting methods over finite fields to show X is Noether-Lefschetz general. We also show that two other divisors considered in [ibid.] are not Noether-Lefschetz divisors.

Topology of real cubic fourfolds

A solution to the problem of topological classification of real cubic fourfolds is presented. It is shown that the real locus of a real non-singular cubic fourfold is obtained from a projective 4-space either by adding several trivial one- and two-handles, or by adding a spherical connected component.