Picard group of the forms of the affine line and of the additive group
  We obtain an explicit upper bound on the torsion of the Picard group of the forms of the affine line and their regular completions. We also obtain a sufficient condition for the Picard group of the forms of the affine line to be non trivial and we give examples of non trivial forms of the affine line with trivial Picard groups. 
Rapha\"el Achet (IF)
math.AG math.GR