A Scheme Independent Definition of $\Lambda_{\rm QCD}$
  Given a renormalization scheme of QCD, one can define a mass scale $\Lambda_{\rm QCD}$ in terms of the beta function. Under a change of the renormalization scheme, however, $\Lambda_{\rm QCD}$ changes by a multiplicative constant. We introduce a scheme independent $\Lambda_{\rm QCD}$ using a connection on the space of the coupling constant. 
Hidenori Sonoda