Rational points of varieties with ample cotangent bundle over function fields of positive characteristic

Abstract

Let $K$ be the function field of a smooth curve over an algebraically closed field $k$. Let $X$ be a scheme, which is smooth and projective over $K$. Suppose that the cotangent bundle ${\Omega }_{X/K}$ is ample. Let $R:=\mathrm{Zar}(X)(K)\cap X)$ be the Zariski closure of the set of all $K$-rational points of $X$, endowed with its reduced induced structure. We prove that there is a projective variety $X_0$ over $k$ and a finite and surjective $K^{\mathrm{sep}}$-morphism $X_{0,K^{\mathrm{sep}}}\to R_{K^{\mathrm{sep}}}$, which is birational when $\mathrm{char}(K)=0$.

Final version; to appear in Mathematische Annalen