I will first introduce K3 surfaces and determine their algebraic deRham cohomology. Next, we will see that crystalline cohomology (no prior knowledge assumed) is the "right" replacement for singular cohomology in positive characteristic. Then, we will look at one particular class of K3 surfaces more closely, namely, supersingular K3 surfaces. These have Picard rank 22 (note: in characteristic zero, at most rank 20 is possible) and form 9-dimensional moduli spaces. For supersingular K3 surfaces, we will see that there exists a period map and a Torelli theorem in terms of crystalline cohomology. As an application of the crystalline Torelli theorem, we will show that a K3 surface is supersingular if and only if it is unirational.[-]

Viehweg and Zuo obtained several results concerning the moduli number in smooth families of polarized varieties with semi-ample canonical class over a quasiprojective base. These results led Viehweg to conjecture that the base of a family of maximal variation is of log-general type, and the conjecture has been recently proved by Campana and Paun.
From the “opposite” side, Taji proved that a smooth projective family over a special (in the sense of Campana) quasiprojective base is isotrivial.
We extend Taji's theorem to quasismooth families, that is, families of leaves of compact foliations without singularities. This is a joint work with F. Campana[-]