Weak matrix elements in the large N{sub c} limit

The matrix elements of the four quark operators needed to predict many weak interaction processes can be evaluated using the large N{sub c} limit of quantum chromodynamics. At leading order in the large N{sub c} expansion, the weak matrix elements of four quark operators factorize into independent matrix elements of two quark operators, a common approximation being used today. At the next leading order, the weak matrix elements acquire the leading scale and scheme dependence expected for these matrix elements in full QCD. They discuss methods to evaluate these matrix elements which involve matching perturbative QCD calculations at short distance to non-perturbative hadronic matrix elements at long distance