 $p>0$
$p>0$Published online by Cambridge University Press: 26 June 2019
In this article, I give a crystalline characterization of abelian varieties amongst the class of smooth projective varieties with trivial tangent bundles in characteristic  $p>0$. Using my characterization, I show that a smooth, projective, ordinary variety with trivial tangent bundle is an abelian variety if and only if its second crystalline cohomology is torsion-free. I also show that a conjecture of KeZheng Li about smooth projective varieties with trivial tangent bundles in characteristic
$p>0$. Using my characterization, I show that a smooth, projective, ordinary variety with trivial tangent bundle is an abelian variety if and only if its second crystalline cohomology is torsion-free. I also show that a conjecture of KeZheng Li about smooth projective varieties with trivial tangent bundles in characteristic  $p>0$ is true for smooth projective surfaces. I give a new proof of a result by Li and prove a refinement of it. Based on my characterization of abelian varieties, I propose modifications of Li’s conjecture, which I expect to be true.
$p>0$ is true for smooth projective surfaces. I give a new proof of a result by Li and prove a refinement of it. Based on my characterization of abelian varieties, I propose modifications of Li’s conjecture, which I expect to be true.
 $\operatorname{Pic}^{\unicode[STIX]{x1D70F}}$. Unpublished, http://www.math.upenn.edu/∼chai/papers_pdf/mumford_ex.pdf.Google Scholar
$\operatorname{Pic}^{\unicode[STIX]{x1D70F}}$. Unpublished, http://www.math.upenn.edu/∼chai/papers_pdf/mumford_ex.pdf.Google Scholar