$\mathbf{\bar{C}_{n,n-1}}$ revisited

Geometry of integers revisited

We study geometry of the ring of integers $O_K$ of a number field $K$. Namely, it is proved that the inclusion $\mathbf{Z}\subset O_K$ defines a covering of the Riemann sphere $\mathbf{C}P^1$ ramified over the points $\{0,1,\infty\}$. Our approach is based on the notion of a Serre $C^*$-algebra. As an application, a new proof of the Belyi Theorem is given.

On the Milnor fibration for $f(\mathbf z)\bar g(\mathbf z)$

We consider a mixed function of type $H(\mathbf z,\bar {\mathbf z})=f(\mathbf z)\bar g(\mathbf z)$ where $f$ and $g$ are convenient holomorphic functions which have isolated critical points at the origin and we assume that the intersection $f=g=0$ is a complete intersection variety with an isolated singlarity at theorigin. We assume also that $H$ satisfies the multiplicity condition.We will show that $H$ has a tubular Milnor fibration and also a spherical Milnor fibration. We give examples which does not satisfy the Newton multiplicity condition where one does not have Milnor fibration and the…

On the Barth-Van de Ven-Tyurin-Sato theorem

The Barth-Van de Ven-Tyurin-Sato Theorem claims that any finite rank vector bundle on the infinite complex projective space $\mathbf{P}^\infty$ is isomorphic to a direct sum of line bundles. We establish sufficient conditions on a locally complete linear ind-variety $\mathbf{X}$ which ensure that the same result holds on $\mathbf{X}$. We then exhibit natural classes of locally complete linear ind-varieties which satisfy these sufficient conditions. Keywords: ind-variety, vector bundle

On the K-theory of truncated polynomial algebras, revisited

We revisit the computation, due to Hesselholt and Madsen, of the K-theory of truncated polynomial algebras for perfect fields of positive characteristic. The resulting K-groups are expressed in terms of big Witt vectors of the field. The original proof relied on an understanding of cyclic polytopes in order to determine the genuine equivariant homotopy type of the cyclic bar construction for a suitable monoid. Using the Nikolaus-Scholze framework for topological cyclic homology we achieve the same result using only the homology of said cyclic bar construction, as well as the action of Connes' …

幂零完备化的p进霍奇理论再探讨

p-adic Hodge theory of unipotent completions revisited

本文针对有限扩张$K/\mathbb{Q}_p$上的代数簇$X$，用棒构造结合Wojtkowiak的方法，证明其幂零完备化的p进霍奇理论相关性质，补充了半稳定、晶态等结论。