canonical which implies imposing In the original AdS/QCD model (section 5.5.1) with the UV cutoff at infin- ity, one finds the decay constants grow as the square root of the excitation number n If one matches g$_{5}$ to the perturbative high energy vector correlator [2,113], giving g 2 5 = 12 π $^{2}$/N$_{c}$ then the ρ$_{0}$ meson has a decay constant F 1 / 2 ρ 0 = 260 MeV compared to the physical value of 345 MeV. In figure 7.2 we display the results of the same computation with a UV cutoff present. For low cutoffs F$_{ρ}$$_{0}$ rises: with Λ = 194 MeV F 1 / 2 ρ 0 = 478 MeV. Comparison with the physical value again hints that a low cutoff is appropriate. On the other hand, as the cutoff is brought down the √$_{n}$ behaviour (argued for in [147]) is apparently lost and the higher resonance decay con- stants fall relative to the n = 0 case. The reason for this is that the cutoff impedes on the values of r where the wave functions of the eigenstates are substantial. By the time that the cutoff is of order a few hundred MeV the integral for the normalization is dominated around the cutoff. This makes the computation of the decay constant suspect - formally one needs a de- scription of the physics to higher energies which may lie beyond the region of perturbative validity for the supergravity. This contrasts with the computation of the masses in the previous section - those values are determined by requiring regular solutions in the infrared away from the cutoff. 101 ∫ Λ 0 dr e − r − 2 rg 2 5 f 2 n = 1 (7.3) F 2 ρ$_{n}$ = 8( n + 1) g 2 5 (7.4)