The Picard Group of Simply Connected Regular Varieties and Stratified   Line Bundles
  We prove that the Picard group of a regular simply connected variety over an algebraically closed field of arbitrary characteristic is finitely generated. The main difficulty to overcome is the unavailability of resolution of singularities. From this we deduce that in positive characteristic there exist no nontrivial stratified line bundles on such a variety, and we present a complex analog. 
Lars Kindler
math.AG