Non-effective Deformations of Grothendieck's Hilbert Functor
Christian Lundkvist, Roy Skjelnes
备注:
8 pages Changed abstract. Fixed typos/grammatical errors. Shortened the introduction. Expanded and clarified Remark 1.9. Shortened the exposition in Section 2 considerably, especially the proof of the first proposition (now Prop 2.3) in this section. Also removed the first lemma (Lemma 2.3) in the section. Added/removed references
Let X be a scheme that does not satisfy the valuative criterion of separatedness. We show that the Hilbert functor parametrizing closed families of X that are flat, finite and of rank one is not represented by a scheme or an algebraic space.
We generalize the adjunction between the functors $Rf_*$ and $f^!$ of derived categories of quasi-coherent sheaves for proper morphisms $f\colon X \to Y$ of Noetherian schemes to the following situation: Let $f$ be a finite type morphism and let $Z' \subseteq X$ and $Z \subseteq Y$ be closed subsets such that $f$ restricts to a proper morphism $f'\colon Z'\to Z$ of $f$. Then the functor $Rf_*$ is left adjoint to $RΓ_{Z'}f^!$ when considered as functors between complexes supported on $Z'$ or $Z$.
We construct a quasi-categorically enhanced Grothendieck six-functor formalism on schemes of finite type over the complex numbers. In addition to satisfying many of the same properties as M. Saito's derived categories of mixed Hodge modules, this new six-functor formalism receives canonical motivic realization functors compatible with Grothendieck's six functors on constructible objects.
We give an explicit stratification of the punctual Hilbert schemes of $n$ points of $\mathbb{A}^{m+1}$ with respect to $m$-dimensional partitions in the Grothendieck group of varieties. As an application, we calculate the classes of the punctual Hilbert schemes of $n$ points of $\mathbb{A}^3$ and the classes of the Hilbert schemes of $n$ points of $\mathbb{A}^3$ in the Grothendieck of varieties for $n\leq 5$.
We construct a functor, from the category of schemes to the category of graded rings, that is an initial object for having a theory of Chern classes with an additive first Chern class. For any scheme $X$, the graded ring that our functor associates to $X$ is related to the associated graded ring of the $γ$-filtration on the Grothendieck ring of finite rank locally free sheaves on $X$ via a Grothendieck-Riemann-Roch type theorem.
对于每个光滑的拟射影曲面X,我们利用导出的McKay对应在n>max{1,1}的Hilbert点方案的导出范畴之间构造一系列P^{n-1}-函子H_{l,n}:D(X x X^[1])--> D(X^[n+1]).它们可以被认为是Nakajima算子的类似物。函子也限于广义Kummer簇上的P^{n-1}-函子。我们还研究了诱导的自等价,并获得,例如,一个普遍的辫子关系的导出自等价的希尔伯特平方的K3曲面和库默尔四倍群。