Chern slopes of surfaces of general type in positive characteristic

Abstract

Let $\mathbb{K}$ be an algebraically closed field of characteristic $p>0$, and let $C$ be a nonsingular projective curve over $\mathbb{K}$. We prove that for any real number $x \geq 2$, there are minimal surfaces of general type $X$ over $\mathbb{K}$ such that a) $c_1^2(X)>0, c_2(X)>0$, b) $\pi_1^{\text{\'et}}(X) \simeq \pi_1^{\text{\'et}}(C)$, c) and $c_1^2(X)/c_2(X)$ is arbitrarily close to $x$. In particular, we show density of Chern slopes in the pathological Bogomolov-Miyaoka-Yau interval $]3,\infty[$ for any given $p$. Moreover, we prove that for $C=\mathbb{P}^1$ there exist surfaces $X$ as above with $H^1(X,\mathcal{O}_X)=0$, this is, with Picard scheme equal to a reduced point. In this way, we show that even surfaces with reduced Picard scheme are densely persistent in $[2,\infty[$ for any given $p$.