Aspects of SU(Nc) gauge theories in the limit of small number of colors

We investigate properties of the color space of SU(N-c) gauge theories in the limit of small numbers (N-c-->0) and large number of flavors. More generally, we introduce a rescaling of alpha(s) and n(f) which assigns a finite limit to colored quantities as N-c-->O, which reproduces their known large-n(c) limit, and which expresses them as an analytic function of N-c(2) for arbitrary value of N-c. The vanishing-N-c limit has an Abelian character and is also the small-N-c limit of [U(1)](Nc-1). This limit does not have an obvious quantum field theory interpretation; however, it provides practical consistency checks on QCD perturbative quantities by comparing them to their QED counterparts. Our analysis also describes the two-dimensional topological structure involved in the interpretation of the small N-c-limit in color space. (C) 1998 Elsevier Science B.V.