Projective geometry for blueprints
  In this note, we generalize the Proj-construction from usual schemes to blue schemes. This yields the definition of projective space and projective varieties over a blueprint. In particular, it is possible to descend closed subvarieties of a projective space to a canonical F_1-model. We discuss this explicitly in case of the Grassmannian Gr(2,4). 
Javier L\'opez Pe\~na and Oliver Lorscheid
math.AG math.AC math.NT