On the geometry of thin exceptional sets in Manin's Conjecture

Freeness alone is insufficient for Manin-Peyre

Manin's conjecture predicts the number of rational points of bounded height on a Fano variety. To make this prediction precise, it is necessary to remove a thin subset of rational points. Peyre has tentatively proposed replacing this subset by the set of points where a certain freeness function he defined takes small values. We show that this proposal fails in the case of $\operatorname{Hilb}^2(\mathbb P^n)$, because the usual thin subset, consisting of rational points that lift to a certain double cover, contains many points with relatively large freeness.

光滑球面 Fano 三维簇的 Manin-Peyre 猜想

The Manin-Peyre conjecture for smooth spherical Fano threefolds

本文证明半单秩一、N 型光滑球面 Fano 三维簇的 Manin-Peyre 猜想，并结合 T 型与环面情形完成所有类型的覆盖。

Manin猜想在弦三次四重流形上的成立

Manin's conjecture for the chordal cubic fourfold

本文证明弦三次四重流形上Manin猜想的薄集版本，通过将其与射影平面的对称平方同构，归结为Schmidt的二次点结果。

Rational curves on del Pezzo surfaces in positive characteristic

We study the space of rational curves on del Pezzo surfaces in positive characteristic. For most primes p we prove the irreducibility of the moduli space of rational curves of a given nef class, extending results of Testa in characteristic 0. We also investigate the principles of Geometric Manin's Conjecture for weak del Pezzo surfaces. In the course of this investigation, we give examples of weak del Pezzo surfaces defined over $\mathbb{F}_{2}(t)$ or $\mathbb{F}_{3}(t)$ such that the exceptional sets in Manin's Conjecture are Zariski dense.

The Batyrev-Tschinkel conjecture for a non-normal cubic surface and its symmetric square

We complete the study of points of bounded height on irreducible non-normal cubic surfaces by doing the point count on the cubic surface $W$ given by $t_0^2 t_2 = t_1^2 t_3$ over any number field. We show that the order of growth agrees with a conjecture by Batyrev and Manin and that the constant reflects the geometry of the variety as predicted by a conjecture of Batyrev and Tschinkel. We then provide the point count for its symmetric square $\mathrm{Sym}^2 W$. Although we can explain the main term of the counting function, the Batyrev--Manin conjecture is only satisfied after removing a thin…

0-闭链的下降障碍与平展-Brauer障碍

Descent and étale-Brauer obstructions for 0-cycles

该研究定义了数域上代数簇0-闭链的下降集与平展-Brauer障碍集，证明其包含于Brauer-Manin集且与Suslin 0次奇异同调相容，将有理点算术研究工具迁移至0-闭链场景并推广Liang的策略到挠子，给出多类代数簇的应用。

Non-semistable exceptional objects in hereditary categories: some remarks and conjectures

In our previous paper we studied non-semistable exceptional objects in hereditary categories and introduced the notion of regularity preserving category, but we obtained quite a few examples of such categories. Certain conditions on the Ext-nontrivial couples (exceptional objects $X,Y\in \mathcal A$ with ${\rm Ext}^1(X,Y)\neq 0$ and ${\rm Ext}^1(Y,X)\neq 0$) were shown to imply regularity-preserving. This paper is a brief review of the previous paper (with emphasis on regularity preserving property) and we add some remarks and conjectures. It is known that in Dynkin quivers ${\rm Hom}(ρ,ρ')=0$…