  We use a perturbative renormalization group approach with short-range
continuum model interactions to analyze the competition between isotropic
gapped and anisotropic gapless ordered states in bilayer graphene, commenting
specifically on the role of exchange and on the importance of spin and valley
flavor degeneracy. By comparing the divergences of the corresponding
susceptibilities, we conclude that this approach predicts gapped states for
flavor numbers N=1,2,4. We also comment briefly on the related gapped states
expected in chiral (ABC) trilayer graphene.
