Ronald van Luijk
For any field k of characteristic at most 5 we exhibit an explicit smooth quartic surface in projective threespace over k with trivial automorphism group over the algebraic closure of k. We also show how this can be extended to higher characteristics. Over the rationals we construct an example on which the set of rational points is Zariski dense.
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Automorphisms of quartic del Pezzo surfaces in characteristic zero
本文对特征零域上四次 del Pezzo 曲面的自同构群进行完整分类，并区分有理、稳定有理与单有理情形，还为每个可实现群给出显式曲面方程。
For every p >= 5, we determine all Z_p-invariant nonsingular quartic surfaces in the three dimensional projective space over an algebraically closed field of characteristic zero. In some cases, we also determine their full projective automorphism groups.
In this work we compute the Dixmier invariants and bitangents of the plane quartics with 3,6 or 9-cyclic automorphisms, we find that a quartic curve with 6-cyclic automorphism will have 3 horizontal bitangents which form an asysgetic triple. We also discuss the linear matrix representation problem of such curves, and find a degree 6 equation of 1 variable which solves the symbolic solution of the linear matrix representation problem for the curve with 6-cyclic automorphism.
Quartic surfaces with an outer Galois point and K3 surfaces with an automorphism of order 4
本文建立了具有外伽罗瓦点的光滑四次曲面与具有特定4阶自同构的K3曲面之间的一一对应，并进一步用K3曲面刻画了具有两个及以上外伽罗瓦点的四次曲面。
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.
We describe a set of generators and defining relations for the group of birational automorphisms of a general 15-nodal quartic surface in the complex projective 3-dimensional space.
Automorphisms of quartic surfaces and Cremona transformations
本文研究光滑四次曲面自同构是否由Cremona变换诱导，在ρ(S)=2时给出初步步骤，构造反例否定Oguiso问题。
This is a continuation of [Og12], concerning automorphisms of smooth quartic K3 surfaces and birational automorphisms of ambient projective three spaces.
Automorphisms of a $(24_4, 32_3)$-configuration on the Schur quartic
研究舒尔四次曲面上(24_4, 32_3)构型的自同构问题，通过特定模型得出24条线一半的稳定子群同构情况及全射影自同构群阶数，还给出内在着色并缩短关联检查。
Sixteen generators of the automorphism group of the Fermat quartic surface
本文解决了复费马四次K3曲面自同构群生成元的长期公开问题，明确给出该群的16个有限阶几何生成元。
We find generators of the group of birational automorphisms of the Hessian surface of a general cubic surface. Its nonsingular minimal model is a K3 surface with the Picard lattice of rank 16. The latter embeds naturally in the even unimodular lattice $II^{1,25}$ of rank 26 and signature $(1,25)$ as the orthogonal complement of a root sublattice of rank 10. Our generators are related to reflections with respect to some Leech roots. A similar observation was made first in the case of quartic Kummer surfaces in the work of S. Kond$\bar {\roman o}$. We shall explain how our generators are related…
Let $S$ be the (minimal) Enriques surface obtained from the symmetric quartic surface $(\sum_{i<j}x_ix_j)^2=kx_1x_2x_3x_4$ in $\mathbb{P}^3$ with $k\neq 0,4,36$, by taking quotient of the Cremona action $(x_i) \mapsto (1/x_i)$. The automorphism group of $S$ is a semi-direct product of a free product $\mathcal{F}$ of four involutions and the symmetric group $\mathfrak{S}_4$. Up to action of $\mathcal{F}$, there are exactly $29$ elliptic pencils on $S$.
On symmetric plane quartic curves
本文研究具有大自同构群的平面四次曲线的几何，重点分析了在$[2,2,2]$型初等阿贝尔群作用下不变的光滑平面四次曲线以及自同构群阶为$48$的光滑平面四次曲线的几何性质。
Automorphism groups of real rational quartic del Pezzo surfaces
本文通过研究实理性四次德尔皮佐表面作为某些光滑实二次曲面的吹胀，描述了所有可能的自同构群，并利用其对复结构的Gal(C/R)作用，给出了实自同构群的几何描述。
Klein's simple group $H$ of order $168$ is the automorphism group of the plane quartic curve $C$, called Klein quartic. By Torelli Theorem, the full automorphism group $G$ of the Jacobian $J=J(C)$ is the group of order $336$, obtained by adding minus identity to $H$. The quotient variety $J/G$ can be alternatively represented as the quotient $\mathbb C^3/\tilde G$ of the complex $3$-space by the complex crystallographic group $\tilde G$, the extension of $G$ by the period lattice of the Klein quartic. Moreover, it turns out that $\tilde G$ is generated by affine complex reflections. According …
It is well-known that a nonsingular minimal cubic surface is birationally rigid; the group of its birational selfmaps is generated by biregular selfmaps and birational involutions such that all relations between the latter are implied by standard relations between reflections on an elliptic curve. It is also known that a factorial nodal quartic threefold is birationally rigid and its group of birational selfmaps is generated by biregular ones and certain birational involutions. We prove that all relations between these involutions are implied by standard relations on elliptic curves, complete …
Let Y be a complex Enriques surface whose universal cover X is birational to a general quartic Hessian surface. Using the result on the automorphism group of X due to Dolgachev and Keum, we obtain a finite presentation of the automorphism group of Y. A fundamental domain of the action of the automorphism group on the nef cone of Y is described explicitly. The list of elliptic fibrations on Y and the list of combinations of rational double points that can appear on a surface birational to Y are presented. As an application, a set of generators of the automorphism group of the generic Enriques s…
We prove some value of the harmonic volume for the Klein quartic $C$ is nonzero modulo ${1/2}\{mathbb Z}$, using special values of the generalized hypergeometric function ${}_3F_2$. This result tells us the algebraic cycle $C-C^-$ is not algebraically equivalent to zero in the Jacobian variety $J(C)$.
Three-dimensional del Pezzo varieties of degree 2 are double covers of projective space $\mathbb{P}^{3}$ branced in a quadric. In this paper we prove that if a del Pezzo variety of degree 2 has exactly 15 nodes then the corresponding quadric is a hyperplane section of the Igusa quartic or, equivalently, all such del Pezzo varieties are members of one particular linear system on the Coble fourfold. Their automorphism groups are induced from the automorphism group of Coble fourfold. Also we classify all $G$-birationally rigid varieties of such type.
We study quartic surfaces that admit a group of projective automorphisms isomorphic to icosahedron group.
Bitangents to symmetric quartics
本文研究亏格三非奇异对称平面四次曲线的自同构群在28条双切线上诱导的对称性，证明了双切线的G-轨道与曲线选择无关，并利用等变同伦理论技术计算了所有十二类曲线的轨道，揭示了经典模视角不明显的模式。
Recently Oguiso showed the existence of K3 surfaces that admit a fixed point free automorphism of positive entropy. The K3 surfaces used by Oguiso have a particular rank two Picard lattice. We show, using results of Beauville, that these surfaces are therefore determinantal quartic surfaces. Long ago, Cayley constructed an automorphism of such determinantal surfaces. We show that Cayley's automorphism coincides with Oguiso's free automorphism. We also exhibit an explicit example of a determinantal quartic whose Picard lattice has exactly rank two and for which we thus have an explicit descript…
The Narasimhan-Nori conjecture asks for a closed formula for the number of non-isomorphic principal polarizations of any given abelian variety. In this paper, we introduce a new algorithm that gives a lower bound on the number of non-isomorphic principal polarizations on any given abelian variety. We show, for example, that the Jacobian of the genus four underlying curve of Schoen's I-WP minimal surface has at least 9 non-isomorphic principal polarizations. We also explore the Jacobians of Klein's quartic, Fermat's quartic, Bring's curve, and more.
We prove that there is a smooth quartic K3 surface automorphism that is not derived from the Cremona transformation of the ambient three-dimensional projective space. This gives a negative answer to a question of Professor Marat Giz.atullin
Tate-Shafarevich results for quartic twists in characteristic $2$
本文研究偶特征函数域上的椭圆曲线，通过具4阶自同构的极大曲线的函数域构造$\u211d_2$上超奇异椭圆曲线的四次扭转，给出由相关曲线亏格表示的Mordell-Weil秩公式，以得到任意大秩的椭圆曲线。
We provide explicit equations of some smooth complex quartic surfaces with many lines, including all 10 quartics with more than 52 lines. We study the relation between linear automorphisms and some configurations of lines such as twin lines and special lines. We answer a question by Oguiso on a determinantal presentation of the Fermat quartic surface.
We consider the class of singular double coverings $X \to \PP^3$ ramified in the degeneration locus $D$ of a family of 2-dimensional quadrics. These are precisely the quartic double solids constructed by Artin and Mumford as examples of unirational but nonrational conic bundles. With such quartic surface $D$ one can associate an Enriques surface $S$ which is the factor of the blowup of $D$ by a natural involution acting without fixed points (such Enriques surfaces are known as nodal Enriques surfaces or Reye congruences). We show that the nontrivial part of the derived category of coherent she…
On Gizatullin's Problem for quartic surfaces of Picard rank $2$
本文研究了 Picard 秩为 $2$ 的一般光滑四次曲面的 Gizatullin 问题，确定了哪些自同构可以限制为 $\mathbb{P}^3$ 的 Cremona 变换。
Action of the automorphism group on the Jacobian of Klein's quartic curve II: Invariant theta functions
本文证明了由反射生成的不可约复晶体反射群在三维复仿射空间上的商是权重为1,2,4,7的加权射影空间，其中相伴共线群是168阶克莱因单群，主要基于不变theta函数代数的计算。
Somos-4 and a quartic Surface in $\mathbb{RP}^{3}$
本文研究Somos-4序列在附加性质下导出的四次多项式，该多项式定义了$\mathbb{RP}^{3}$中的有理射影曲面，并确定了其双有理自同构所在的$Cr_3(\mathbb{R})$子群的生成元。
Let X be an irreducible smooth projective curve, of genus at least two, defined over an algebraically closed field of characteristic different from two. If X admits a nontrivial automorphism σthat fixes pointwise all the order two points of Pic}^0(X), then we prove that X is hyperelliptic with σbeing the unique hyperelliptic involution. As a corollary, if a nontrivial automorphisms σ' of X fixes pointwise all the theta characteristics on X, then X is hyperelliptic with σ' being its hyperelliptic involution.
Automorphism groups of curves with simple Jacobians
研究特征为0的代数闭域上具有简单雅可比矩阵的光滑射影连通曲线的自同构群，通过构造曲线族并证明其密度为1的成员集有简单雅可比矩阵，在主极化阿贝尔簇模空间中给出无限多个新的不太可能的交的例子。
We classify all possible automorphism groups of smooth cubic surfaces over an algebraically closed field of arbitrary characteristic. As an intermediate step we also classify automorphism groups of quartic del Pezzo surfaces. We show that the moduli space of smooth cubic surfaces is rational in every characteristic, determine the dimensions of the strata admitting each possible isomorphism class of automorphism group, and find explicit normal forms in each case. Finally, we completely characterize when a smooth cubic surface in positive characteristic, together with a group action, can be lift…
A generalisation of the pencil of Kuribayashi-Komiya quartics
本文将 Kuribayashi-Komiya 四次曲线束推广到素数 p≥5 的情形，确定广义曲线束光滑成员的完全自同构群及其作用，证明无超椭圆成员，并分类具有相同自同构群的亏格 (p-1)(2p-1) 黎曼曲面。
Pseudo-automorphisms of rational threefolds and Kummer surfaces
本文将45个经典Kummer曲面自同构提升为$\mathbb{P}^3$沿6点15线爆破所得三维簇的伪自同构，并描述了由这些已知伪自同构生成的群的基本域。
We explain a classical construction of a del Pezzo surface of degree d = 4 or 5 as a smooth order two congruence of lines in 3-space whose focal surface is a quartic surface $X_{20-d}$ with 20-d ordinary double points. We also show that $X_{15}$ can be realized as a hyperplane section of the Castelnuovo-Richmond-Igusa quartic hypersurface. This leads to the proof of rationality of the moduli space of 15-nodal quartic surfaces. We discuss some other birational models of $X_{15}$: quartic symmetroids, 5-nodal quartic surfaces, 10-nodal sextic surfaces in $P^4$ and nonsingular surfaces of degree …
For each finite primitive subgroup $G$ of $\operatorname{PGL}_4(\mathbb{C})$, we find all the smooth $G$-invariant quartic surfaces. We also find all the faithful representations in $\operatorname{PGL}_4(\mathbb{C})$ of the smooth quartic $G$-invariant surfaces by the groups: $\mathfrak{A}_5,\mathfrak{S}_5, \operatorname{PSL_2(\mathbb{F}_7)},\mathfrak{A}_6,\mathbb{Z}_2^4\rtimes\mathbb{Z}_5$ and $\mathbb{Z}_2^4\rtimes D_{10}$. The primitive representation of these groups are precisely the subgroups of $\operatorname{PGL}_4(\mathbb{C})$ for which $\mathbb{P}^3$ is not $G$-super rigid. As a bypro…
On arrangements of smooth plane quartics and their bitangents
本文从多视角重新探讨光滑平面四次曲线及其二重切线的几何性质，研究高度对称四次曲线二重切线排列的弱组合学，为Ciani pencil光滑成员的二重切线排列四重交点数建立下界，并构造3-合冲约化平面曲线新例子。
On two-elementary K3 surfaces with finite automorphism group
本研究针对皮卡秩11-13、带有限自同构群和二阶截面雅可比椭圆纤维化的复代数K3曲面，证明其存在射影四次超曲面双有理模型，构造椭圆纤维化标架，确定有理曲线对偶图等几何结构。
Automorphisms of very general blow up
该研究证明，维数≥2且非有理曲面的射影簇在足够多非常一般的点处的爆破，不存在非平凡自同构，补充了ℙ²、ℙ³之外的相关结果。
Desmic quartic surfaces in arbitrary characteristic
研究Desmic四次曲面作为椭圆曲线自积的Kummer曲面的双有理模型，在任意特征下推广其经典几何，并证明关联的三次线丛是有34个节点的有理Fano三维流形。
We show, for several fake projective planes with nontrivial automorphism group, that the bicanonical map is an embedding.
We investigate the action of the automorphism group of a closed Riemann surface on its set of theta characteristics (or spin structures). We give criteria for when an automorphism fixes all spin structures, or when it fixes just one. The case of hyperelliptic curves and of the Klein quartic are discussed in detail.
The $a$-numbers of non-hyperelliptic curves of genus 3 with cyclic automorphism group of order 6
本文研究了具有阶为6循环自同构群的亏格3非超椭圆曲线，给出了其同构的充分必要条件，并利用高斯超几何级数描述Hasse-Witt矩阵，确定了可能的$a$-数及达到最大$a$-数的同构类数量。
Two families of surfaces arise from considering cyclic branched covers of $\mathbb{P}^{2}$ over smooth quartic curves. These consist of degree 2 del Pezzo surfaces with a $\mathbb{Z}/2\mathbb{Z}$ action and $K3$ surfaces with a $\mathbb{Z}/4\mathbb{Z}$ action. We compute the monodromy groups of both families. In the first case, we obtain the Weyl group $W\left(E_{7}\right)$, corresponding to the automorphisms of the $56$ lines contained in a degree $2$ del Pezzo surface. In the second case we obtain an arithmetic lattice: the unitary group $U\left(h_{L_{-}}\right)$ of a type $\left(1, 6\right)…
Motivated by an application to LDPC (low density parity check) algebraic geometry codes described by Voloch and Zarzar, we describe a computational procedure for establishing an upper bound on the arithmetic or geometric Picard number of a smooth projective surface over a finite field, by computing the Frobenius action on p-adic cohomology to a small degree of p-adic accuracy. We have implemented this procedure in Magma; using this implementation, we exhibit several examples, such as smooth quartics over F_2 and F_3 with arithmetic Picard number 1, and a smooth quintic over F_2 with geometric …
Nikulin and Vinberg proved that there are only a finite number of lattices of rank $\geq 3$ that are the Néron-Severi group of projective K3 surfaces with a finite automorphism group. The aim of this paper is to provide a more geometric description of such K3 surfaces $X$, when these surfaces have moreover no elliptic fibrations. In that case we show that such K3 surface is either a quartic with special hyperplane sections or a double cover of the plane branched over a smooth sextic curve which has special tangencies properties with some lines, conics or cuspidal cubic curves. We then study th…
We describe a normal form for a smooth intersection of two quadrics in even-dimensional projective space over an arbitrary field of characteristic 2. We use this to obtain a description of the automorphism group of such a variety. As an application, we show that every quartic del Pezzo surface over a perfect field of characteristic 2 has a canonical rational point and, thus, is unirational.
On the $K3$ surface with $\mathfrak{S}_4 \times \mathfrak{S}_4$ action
本文通过格论方法研究了具有 $\mathfrak{S}_4 \times \mathfrak{S}_4$ 行动的 $K3$ 表面，提供了三种显式描述，并计算了两个极化保持有限自同构群的交集。
Let $S$ be a minimal smooth projective surface of general type with irregularity $q=2$. We show that, if $S$ has a nontrivial holomorphic automorphism acting trivially on the cohomology with rational coefficients, then it is a surface isogenous to a product. As a consequence of this geometric characterization, one infers that no nontrivial automorphism of surfaces of general type with $q=2$ (which are not necessarily minimal) can be homotopic to the identity. In particular, such surfaces are rigidified in the sense of Fabrizio Catanese.
It has been proved several times in the literature that a polynomial map from $C^2$ to $C$ with irreducible rational fibers cannot be a component of a counterexample to the Jacobian Conjecture. This note points out that this result is empty: it is implicit in 1980 work of Miyanish and Sugie that such a polynomial is equivalent to $f(x,y)=x$ by a polynomial automorphism of $C^2$.
Jacobian conjectures (that nonsingular implies invertible) for rational everywhere defined maps of real n-space to itself are considered, with no requirement for a constant Jacobian determinant or a rational inverse. The associated extension of rational function fields must be of odd degree and must have no nontrivial automorphisms. The extensions for the Pinchuk counterexamples to the strong real Jacobian conjecture have no nontrivial automorphisms, but are of degree six. The birational case is proved, the Galois case is clarified but the general case of odd degree remains open. However, cert…
Automorphisms of the moduli space of smooth cubic surfaces and its fundamental group
研究光滑三重曲面模空间的基本群，证明其除子子群是特征子群，并推导出该空间无非平凡复解析轨道自同构。
Cohomologically or numerically trivial automorphisms of surfaces of general type
本文研究一般型表面的上同调和数值上平凡自同构，确定了可约假二次曲面的群结构，并给出了具有特定自同构群的表面实例。
The Einstein-Weyl spaces associated to Segre quartic surfaces
本研究找到亏格1的Segre四次曲面对应的紧致迷你扭量空间显式例子，其Einstein-Weyl空间的连通分支微分同胚于de Sitter空间，结构随Segre曲面形变并收敛到标准de Sitter结构，还借助曲面实节点构造了不可紧化的非紧复曲面例子。
On projective K3 surfaces $\mathcal{X}$ with $\mathrm{Aut}(\mathcal{X})=(\mathbb{Z}/2\mathbb{Z})^2$
该数学代数几何领域的研究证明了自同构群为$(\mathbb{Z}/2\mathbb{Z})^2$的K3曲面存在双六次曲面形式的显式双有理模型，还在皮卡数大于9时得到推广Inose四次曲面的射影四次超曲面第二模型。
The Getzler's formula relates the S_n-equivariant Hodge-Deligne polynomial of the space of ordered tuples of distinct points on a given variety X with the Hodge-Deligne polynomial of X. We obtain the analogue of this formula for the case when X has a nontrivial automorphism group. Collecting together all strata of $\mathcal{M}_2$ with different automorphism groups, we derive a formula for the S_n-equivariant Euler characteristic of $\mathcal{M}_{2,n}$.
The elliptic modular surface of level 4 is a complex K3 surface with Picard number 20. This surface has a model over a number field such that its reduction modulo 3 yields a surface isomorphic to the Fermat quartic surface in characteristic 3, which is supersingular. The specialization induces an embedding of the Néron-Severi lattices. Using this embedding, we determine the automorphism group of this K3 surface over a discrete valuation ring of mixed characteristic whose residue field is of characteristic 3. The elliptic modular surface of level 4 has a fixed-point free involution that gives r…
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