  At zero density, the `t Hooft large N_c limit often provides some very useful
qualitative insights into the non-perturbative physics of QCD. However, it is
known that at high densities the `t Hooft large N_c world looks very different
from the N_c=3 world, which is believed to be in a color superconducting phase
at high densities. At large N_c, on the other hand, the DGR instability causes
a chiral-density wave phase to dominate over the color superconducting phase.
There is an alternative large N_c limit, with the quarks transforming in the
two-index antisymmetric representation of the gauge group, which at N_c=3
reduces to QCD but looks quite different at large N_c. We show that in this
alternative large N_c limit, the DGR instability does not occur, so that it may
be plausible that the ground state of high-density quark matter is a color
superconductor even when N_c is large. This revives the hope that a large N_c
approximation might be useful for getting some insights into the high-density
phenomenology of QCD.
