Supersingular K3 surfaces in odd characteristic and sextic double planes

Dynkin diagrams of rank 20 on supersingular K3 surfaces

We classify normal supersingular K3 surfaces Y with total Milnor number 20 in characteristic p, where p is an odd prime that does not divide the discriminant of the Dynkin type of the rational double points on Y.

On certain duality of Néron-Severi lattices of supersingular K3 surfaces

Let X and Y be supersingular K3 surfaces defined over an algebraically closed field. Suppose that the sum of their Artin invariants is 11. Then there exists a certain duality between their Néron-Severi lattices. We investigate geometric consequences of this duality. As an application, we classify genus one fibrations on supersingular K3 surfaces with Artin invariant 10 in characteristic 2 and 3, and give a set of generators of the automorphism group of the nef cone of these supersingular K3 surfaces. The difference between the automorphism group of a supersingular K3 surface X and the automorp…

属五 Howe 曲线的平面六次模型的显式构造，II

Explicit construction of a plane sextic model for genus-five Howe curves, II

本文构造了属五非超椭圆 Howe 曲线的显式平面六次模型，确定其奇点一般为四个二重点，并结合已有结果证明存在具有不同二重点数的曲线族。

奇特征下超奇异 K3 曲面的辛自同构有限群

Finite Groups of Symplectic Automorphisms of Supersingular K3 surfaces in Odd Characteristics

本文利用格理论方法研究奇特征下有限群在 K3 曲面上的辛作用，提出 p-根对机制约束超奇异 K3 曲面的非温顺辛作用，并给出群阶中 p 的指数上界。

奇特征下超奇异阿贝尔簇的Oort猜想

Oort's conjecture on supersingular abelian varieties in odd characteristic

针对奇特征p>2，构造含a不变量g-2开稠密集的闭子簇，为Oort猜想提供独立证明，补充了Viehmann对a=1轨迹的研究。

The Number of Rational Points On Genus 4 Hyperelliptic Supersingular Curves in Characteristic 2

One of the big questions in the area of curves over finite fields concerns the distribution of the numbers of points: Which numbers occur as the number of points on a curve of genus $g$? The same question can be asked of various subclasses of curves. In this article we classify the possibilities for the number of points on genus 4 hyperelliptic supersingular curves over finite fields of order $2^n$, $n$ odd.

Tritangents and Their Space Sextics

Two classical results in algebraic geometry are that the branch curve of a del Pezzo surface of degree 1 can be embedded as a space sextic curve and that every space sextic curve has exactly 120 tritangents corresponding to its odd theta characteristics. In this paper we revisit both results from the computational perspective. Specifically, we give an algorithm to construct space sextic curves that arise from blowing up projective plane at eight points and provide algorithms to compute the 120 tritangents and their Steiner system of any space sextic. Furthermore, we develop efficient inverses …

关于正特征域上阿贝尔簇的Fourier-Mukai伙伴的一个注记

A note on Fourier-Mukai partners of abelian varieties over positive characteristic fields

本文研究正特征域上阿贝尔簇的Fourier-Mukai伙伴，将Krug-Sosna关于Kummer栈的导出等价结果推广到奇特征情形，证明阿贝尔曲面导出等价与Kummer曲面同构等价，并建立超奇异阿贝尔簇的导出Torelli定理。

Dynamics on supersingular K3 surfaces

For any odd characteristic p=2 mod 3, we exhibit an explicit automorphism on the supersingular K3 surface of Artin invariant one which does not lift to any characteristic zero model. Our construction builds on elliptic fibrations to produce a closed formula for the automorphism's characteristic polynomial on second cohomology, which turns out to be an irreducible Salem polynomial of degree 22 with coefficients varying with p.

A lifting of an automorphism of a K3 surface over odd characteristic

In this paper, we prove that, over an algebraically closed field of odd characteristic, a weakly tame automorphism of a K3 surface of finite height can be lifted over the ring of Witt vectors of the base field. Also we prove that a non-symplectic tame automorphism of a supersingular K3 surface or a symplectic tame automorphism of a supersingular K3 surface of Artin-invariant at least 2 can be lifted over the ring of Witt vectors. Using these results, we prove, for a weakly tame K3 surface of finite height, there is a lifting over the ring of Witt vectors to which whole the automorphism group o…

与超奇异阿贝尔曲面的Moret-Bailly族相关联的同源图

Isogeny graphs associated to Moret-Bailly families of supersingular abelian surfaces

研究特征p下阿贝尔曲面的Moret-Bailly族等价类与相对(ℓ,ℓ)-同源构成的有限有向图，将其与GSp₄/ℚ的内形式上的代数模形式空间关联，并利用Jacquet-Langlands对应估计邻接矩阵的特征值。

Numerically trivial automorphisms of Enriques surfaces in characteristic $2$

An automorphism of an algebraic surface $S$ is called cohomologically (numerically) trivial if it acts identically on the second $l$-adic cohomology group (this group modulo torsion subgroup). Extending the results of S. Mukai and Y. Namikawa to arbitrary characteristic $p > 0$, we prove that the group of cohomologically trivial automorphisms $\rm{Aut}_{\rm{ct}}(S)$ of an Enriques surface $S$ is of order $\leq 2$ if $S$ is not supersingular. If $p = 2$ and $S$ is supersingular, we show that $\rm{Aut}_{\rm{ct}}(S)$ is a cyclic group of odd order $n\in \{1,2,3,5,7,11\}$ or the quaternion group $…

Odd order obstructions to the Hasse principle on general K3 surfaces

We show that odd order transcendental elements of the Brauer group of a K3 surface can obstruct the Hasse principle. We exhibit a general K3 surface $Y$ of degree 2 over $\mathbb{Q}$ together with a three torsion Brauer class $α$ that is unramified at all primes except for 3, but ramifies at all 3-adic points of $Y$. Motivated by Hodge theory, the pair $(Y, α)$ is constructed from a cubic fourfold $X$ of discriminant 18 birational to a fibration into sextic del Pezzo surfaces over the projective plane. Notably, our construction does not rely on the presence of a central simple algebra represen…