How large is large Nc for nuclear matter?

We argue that a so far neglected dimensionless scale, the number of neighbors in a closely packed system, is relevant for the convergence of the large-N (c) expansion at high chemical potential. It is only when the number of colors is large w.r.t. this new scale that a convergent large-N (c) limit is reached. This provides an explanation as to why the large-N (c) expansion, qualitatively successful in vacuum QCD, fails to describe high baryo-chemical potential systems, such as nuclear matter. It also means that phenomenological claims about high-density matter based on large-N (c) extrapolations should be treated with caution. This work is based on [1].