Towards a perfect QCD gravity dual

Many examples of gravitational duals exist of theories that are highly supersymmetric and conformal in the UV yet have the same massless states as N = 2, 1, 0 QCD. We discuss such theories with an explicit UV cutoff and propose that, by tuning higher dimension operators at the cutoff by hand, the effects of the extra matter states in the UV may be removed from the IR physics. We explicitly work in the AdS-Schwarzschild description of QCD(4) and tune the operator Tr F-4 by relaxing the near horizon limit to reproduce the lattice 0(++) glueball mass results. We find that to reproduce the lattice data, the IR and UV cutoffs lie close to each other and there is essentially no AdS-like period between them. The improved geometry gives a better match to the lattice data for 0(-+) glueball masses. (c) 2005 Elsevier B.V. All rights reserved.