(non)commutative f-un geometry.

link: http://arxiv.org/abs/0909.2522
Abstract

Stressing the role of dual coalgebras, we modify the definition of affine
schemes over the 'field with one element'. This clarifies the appearance of
Habiro-type rings in the commutative case, and, allows a natural noncommutative
generalization, the study of representations of discrete groups and their
profinite completions being our main motivation.