  Using holography, we study the low-lying mesonic spectrum of a range of
asymptotically free gauge theories. First we revisit a simple top-down
holographic model of QCD-like dynamics with predictions in the M_rho-M_pi
plane. The meson masses in this model are in very good agreement with lattice
gauge theory calculations in the quenched approximation. We show that the key
ingredient for the meson mass predictions is the running of the anomalous
dimension of the quark condensate, gamma. This provides an explanation for the
agreement of holographic and quenched lattice gauge theory calculations. We
then study the `Dynamic AdS/QCD model' in which the gauge theory dynamics is
included by a choice for the running of gamma. We use the naive two-loop
perturbative running of the gauge coupling extrapolated to the non-perturbative
regime to estimate the running of gamma across a number of theories. We
consider models with quarks in the fundamental, adjoint, two-index symmetric
and two-index anti-symmetric representations. We display predictions for M_rho,
M_pi, M_sigma and the lightest glueball mass. Many of these theories, where the
contribution to the running of gamma is dominated by the gluons, give very
similar spectra, which also match with lattice expectations for QCD. On the
other hand, a significant difference between spectra in different holographic
models is seen for theories where the quark content changes the gradient of the
running of gamma around the scale at which chiral symmetry breaking is
triggered at gamma approximately 1. For these walking theories we see an
enhancement of the rho-mass and a suppression of the sigma-mass. Both phenomena
are characteristic for walking behaviour in the physical meson masses.
