6.2.4 Conclusions In section 5.2 we pointed out that the perturbative matching of g$_{5}$ may not be ideal. So once again, we have performed a fit with g$_{5}$ being considered as a extra free parameter. This indicated that the optimal value of g$_{5}$ is 4.36, which is 18% higher than 3.54, the value suggested by the perturbative- matching result in equation (5.12). g$_{5}$ coupling We have adapted a string theoretic model of chiral symmetry breaking to a phenomenological description of QCD. The model we have proposed goes some way towards addressing the inconsistencies of simple AdS slice holo- graphic QCD models [2,113]. The background geometry of our model is non- supersymmetric, and it is the smooth variation of this geometry with the radial direction r that provides a mass gap, without the need for an artificial hard IR cut-off. In addition, the dual field to the quark mass/condensate operator is a natural part of the geometrical set-up with the value of the condensate being determined by the quark mass. However, this is still a phenomenological approach in that we introduce extra fields and symmetries by hand into the model in order to describe the full pion and axial vector sectors. Formally there is no geometric string interpretation for this system. We also treat the background as though it describes an N = 3 rather than an N = ∞ field theory by matching the 5D gauge coupling to QCD. We find that the predictions of this model match experimental results to within 12%. This model is a little more predictive than the pure AdS slice models since the condensate is dynamically determined by the geometry. The best fit is in fact a few percent worse than the AdS slice models but 95