Some aspects of non-perturbative QCD from non-susy D3 brane of Type IIB string theory

It is well-known that the non-supersymmetric D3 brane (a cousin of BPS D3 brane) including its black version of type IIB string theory has a decoupling limit, where the decoupled geometry is the gravity dual of a non-supersymmetric, non-conformal (finite temperature) quantum field theory having some properties similar to QCD. Using the ideas of AdS/CFT we study some non-perturbative aspects of this quantum field theory. Since in this case we have a Yang-Mills theory (no quarks) with running coupling (non-constant dilaton), we compute the gluon condensate in this theory as a function of temperature and also compute the beta function. The behavior of the gluon condensate is found to resemble much like the SU(3) lattice QCD result and the beta function is found to be negative. We further compute both the pseudoscalar and the scalar glueball mass spectra in this theory using WKB approximation and find that the mass ratios of the first excited state to the ground state of the scalar glueball are quite close to the lattice QCD results.