In the last 60 years, the use of the notion of category has led to a remarkable unification and simplification of mathematics. Conceptual Mathematics, He proposed elementary book is presented, inâ€¦ (More)

According to Bass-Serre theory [Se], given a field F with a discrete valuation v : F âˆ—â†’Z, there is a canonical way to construct a simplicial tree T = TF,v on whichSL2(F ) acts simplicially withoutâ€¦ (More)