On the Couplings of Vector Mesons in AdS/QCD

We address, in the AdS/CFT context, the issue of the universality of the couplings of the ρ meson to other hadrons. Exploring some models, we find that generically the ρ-dominance prediction fρgρHH mρ2 does not hold, and that gρHH is not independent of the hadron H. However, we prove that, in any model within the AdS/QCD context, there are two limiting regimes where the gρHH, along with the couplings of all excited vector mesons as well, become H-independent: (1) when H is created by an operator of large dimension, and (2) when H is a highly-excited hadron. We also find a sector of a particular model where universality for the ρ coupling is exact. Still, in none of these cases need it be true that fρgρ = mρ2, although we find empirically that the relation does hold approximately (up to a factor of order two) within the models we have studied