Don’t be fooled by introductory remarks to the effect that ‘the field with one element was conceived by Jacques Tits…’ Let’s have it out into the open : F_un mathematics’ goal is no less than proving the Riemann Hypothesis.

Grothendieck’s anabelian geometry is an example of noncommutative F_un geometry. Javier starts this series with ramblings on how the folklore about F_un can be used to relate linear and permutation representations of finite groups.

Alain Connes and Katia Consani arXived the paper “On the notion of geometry over F_un” in which they refine and simplify Soule’s approach. This series tries to explain their construction to non-specialists in algebraic geometry.

Any possible definition of a variey over F_un should have a nice extension of scalars to the integers. In particular, we might expect to be able to control the behavior of such extension for the easiest family of rings defined over F_un: its finite abelian extensions F_un^n.

To Gavin Wraiht a mathematical phantom is a “nonexistent entity which ought to be there but apparently is not; but nevertheless obtrudes its effects so convincingly that one is forced to concede a broader notion of existence”. Mathematics’ history is filled with phantoms getting the kiss of life.

In recent years several people spend a lot of energy looking for properties of an elusive object : the field with one element or in French : “F-un”. One of the motivations is the hope to prove the Riemann hypothesis by mimicking Weil’s proof in the case of curves.