Let X be a supersingular K3 surface in characteristic 5 with Artin invariant 1. Then X has a polarization that realizes X as the Fermat sextic double plane. We present a list of polarizations of X with degree 2 whose intersection number with this Fermat sextic polarization is less than or equal to 5, and give the defining equations of the corresponding projective models. We also present a method to describe birational morphisms between these projective models explicitly. As a by-product, a non-projective automorphism of the Fermat sextic double plane is obtained.
We give a short proof that every supersingular K3 surface (except possibly in characteristic $2$ with Artin invariant $σ=10$) has an automorphism of Salem degree 22. In particular an infinite subgroup of the automorphism group does not lift to characteristic zero. The proof relies on the case $σ=1$ and the cone conjecture for K3 surfaces.
The automorphism group of a supersingular K3 surface with Artin invariant 1 in characteristic 3
Graduate School of Mathematics, Nagoya University（名古屋大学大学院数学研究科）；Department of Mathematics, Graduate School of Science, Hiroshima University（广岛大学理学研究科数学系）
We show that most classes of K3 surfaces have only finitely many Enriques quotients. For supersingular K3 surfaces over fields of characteristic $p \geq 3$, we give a formula which generically yields the number of their Enriques quotients. We reprove via a lattice theoretic argument that supersingular K3 surfaces always have an Enriques quotient over fields of small characteristic. For some small characteristics and some Artin invariants, we explicitly compute lower bounds for the number of Enriques quotients of a supersingular K3 surface. We show that the supersingular K3 surface of Artin inv…
O'Grady constructed a 6-dimensional irreducible holomorphic symplectic variety by taking a crepant resolution of some moduli space of stable sheaves on an abelian surface. In this paper, we naturally extend O'Grady's construction to fields of positive characteristic p greater than 2, called OG6 varieties. We show that a supersingular OG6 variety is unirational, its rational cohomology group is generated by algebraic classes, and its rational Chow motive is of Tate type. These results confirm in this case the generalized Artin--Shioda conjecture, the supersingular Tate conjecture and the supers…
We describe a method to show that certain elliptic surfaces do not admit purely inseparable multisections (equivalently, that genus one curves over function fields admit no points over the perfect closure of the base field) and use it to show that any non-Jacobian elliptic structure on a very general supersingular K3 surface has no purely inseparable multisections. We also describe specific examples of such fibrations without purely inseparable multisections. Finally, we discuss the consequences for the claimed proof of the Artin conjecture on unirationality of supersingular K3 surfaces.
The action of the Frobenius map on rank 2 vector bundles over a supersingular genus 2 curve in characteristic 2
设$X$是特征为2的代数闭域上的光滑真亏格2曲线.绝对Frobenius在$X$上半稳定秩为2的向量丛的模空间$M\_X$上诱导出一个有理映射$F$，它同构于一个三维射影空间. Y. Laszlo和C. Pauly最近给出了普通$X$的$F$方程。利用变形，我们给出了超奇异$X$的这些方程，并得出了一些结论，如$F$的基轨迹（一点），或互补Zaplski开集的稳定性.
Mathematisches Institut, Universität Bonn（波恩大学数学研究所）；TUM School of Computation, Information and Technology, Department of Mathematics (M11), Technische Universität München（慕尼黑工业大学计算、信息与技术学院数学系）
The arrangement of all Galois lines for the Artin-Schreier-Mumford curve in the projective 3-space is described. It may be surprising that there exist infinitely many Galois lines intersecting this curve.
Artin-Schreier geproci configurations in projective spaces of arbitrary dimension
Dipartimento di Ingegneria dell’Informazione e Scienze Matematiche, Università di Siena（锡耶纳大学）；Department of Mathematics, University of the National Education Commission（国家教育委员会大学）；Dipartimento di Ingegneria, Università degli Studi di Palermo（巴勒莫大学）；Department of Mathematics, University of Nebraska–Lincoln（内布拉斯加大学林肯分校）；Department of Mathematics, University of Notre Dame（圣母大学）
