On $q$-complete and $q$-concave with corners complex manifolds

TL;DR

This paper investigates the relationship between $q$-completeness and cohomological $q$-completeness in complex manifolds, providing counterexamples and new results that clarify their differences and connections.

Contribution

It constructs counterexamples to the conjecture that cohomological $q$-completeness implies $q$-completeness, and demonstrates the existence of $q$-complete with corners sets that are not cohomologically $ ilde{q}$-complete.

Findings

Counterexample to Andreotti-Grauert conjecture.

Existence of $q$-complete with corners sets not cohomologically $ ilde{q}$-complete.

Clarification of the distinction between $q$-completeness and cohomological $q$-completeness.

Abstract

It is proved that if there exists a positive and continuous function $f$ on an $n$-dimensional complex manifold $X$, $q$-convex with corners outside a compact set $K\subset X$ and which exhausts $X$ from below, then $dim_{\mathbb{C}}H^{p}(X,{\mathcal{F}})<+\infty$ for any coherent analytic sheaf ${\mathcal{F}}$ on $X$ if $p<n-q$. It is known from the theory of Andreotti and Grauert that if a complex space $X$ is $q$-complete, then $X$ is cohomoloogically $q$-complete. Until now it is not known in general if these two conditions are equivalent. The aim of section $4$ of this article is to provide a counterexample to the conjecture posed by Andreotti and Grauert ~\cite{ref2} to show that a cohomologically $q$-complete space is not necessarily $q$-complete. In section $5$ of this article, we will prove that there exist for each pair of integers $(n,q)$ with $2\leq q\leq n-1$ a $q$-complete with corners open subset $D$ of $\mathbb{P}^{n}$ and $\mathcal{F}\in coh(\mathbb{P}^{n})$ such that $D$ is not cohomologically $\hat{q}$-complete with respect to ${\mathcal{F}}$. Here $\hat{q}=n-[\frac{n-1}{q}]$, where $[x]$ denotes the integral part of $x$.