QCD quark condensate from SUSY and the orientifold large-N expansion

We estimate the quark condensate in one-flavor massless QCD from the known value of the gluino condensate in SUSY Yang-Mills theory using our newly proposed orientifold large-N expansion. The numerical result for the quark condensate renormalized at the scale 2 GeV is then given as a function of alpha(s) (2 GeV) and of possible corrections from sub-leading terms. Our value can be compared with the quark condensate in (quenched) lattice QCD or with the one extracted from the Gell-Mann-Oakes-Renner relation by virtue of non-lattice determinations of the quark masses. In both cases we find quite a remarkable agreement. (C) 2003 Elsevier B.V. All rights reserved.