Gauss-Manin stratification and stratified fundamental group schemes

Stratified Bundles on Curves and Differential Galois Groups in Positive Characteristic

Stratifications and iterative differential equations are analogues in positive characteristic of complex linear differential equations. There are few explicit examples of stratifications. The main goal of this paper is to construct stratifications on projective or affine curves in positive characteristic and to determine the possibilities for their differential Galois groups. For the related "differential Abhyankar conjecture" we present partial answers, supplementing the literature. The tools for the construction of regular singular stratifications and the study of their differential Galois g…

About the cohomological dimension of certain stratified varieties

We determine an upper bound for the cohomological dimension of the complement of a closed subset in a projective variety which possesses an appropriate stratification. We apply the result to several particular cases, including the Bialynicki-Birula stratification; in this latter case, the bound is optimal.

Incidence stratifications on Hilbert schemes of smooth surfaces, and an application to Poisson structures

Given a smooth curve on a smooth surface, the Hilbert scheme of the surface is stratified according to the length of the intersection with the curve. The strata are highly singular. We show that this stratification admits a natural log-resolution, namely the stratified blowup. As a consequence, the induced Poisson structure on the Hilbert scheme of a Poisson surface has unobstructed deformations.

Stratified-algebraic vector bundles

We investigate stratified-algebraic vector bundles on a real algebraic variety X. A stratification of X is a finite collection of pairwise disjoint, Zariski locally closed subvarieties whose union is X. A topological vector bundle on X is called a stratified-algebraic vector bundle if, roughly speaking, there exists a stratification of X such that the restriction of the bundle to each stratum is an algebraic vector bundle. In particular, every algebraic vector bundle on X is stratified-algebraic. It turns out that stratified-algebraic vector bundles have many surprising properties, which disti…

带孤立奇点的簇的导出分层与算术相交理论

Derived Stratifications and Arithmetic Intersection Theory for Varieties with Isolated Singularities

本文针对带孤立奇点的簇，用导出几何等工具建立分层德拉姆理论，统一拓展相关理论框架，并填补Ohsawa证明的缺口，验证Cheeger-Goresky-MacPherson猜想的相关结论。

A Kazhdan-Lusztig Atlas on G/P

A stratified variety has a Kazhdan-Lusztig atlas if it can be locally modelled with Kazhdan-Lusztig varieties stratified by Schubert varieties in some Kac-Moody flag manifold via stratified isomorphisms. In this paper, we show that the partial flag manifold $G/P$ with the projected Richardson stratification has a Kazhdan-Lusztig atlas, with each chart stratified-isomorphic to a Kazhdan-Lusztig variety in the affine flag manifold of the formal loop group $\widehat{G}$ of $G$. This result generalizes that of Snider's on $Gr(k,n)$ with the positroid stratification, and is a geometric counterpart …