Calabi-Yau threefolds in positive characteristic
arXiv:1701.07593
Abstract
In this note, an overview of Calabi-Yau varieties in positive characteristic is presented. Although Calabi-Yau varieties in characteristic zero are unobstructed, there are examples of Calabi-Yau threefolds in positive characteristic which cannot be lifted to characteristic zero, although one-dimensional and two-dimensional Calabi-Yau varieties, i.e., elliptic curves and K3 surfaces, are all liftable to characteristic zero. In this respect, Calabi-Yau threefolds in positive characteristic are interesting in view of deformation theory and they are still very mysterious.
Expanded lecture notes of a course given as part of XVI International Workshop for Young Mathematicians "Algebraic Geometry" held in Krakow, September 18 -- 24, 2016