Three-loop beta function and non-perturbative $α_s$ in asymmetric momentum scheme

We determine the three-loop coefficient of the beta function in the asymmetric momentum subtraction scheme in Landau gauge. This scheme is convenient for lattice studies of $\alpha_s$, the running coupling constant of QCD. We present high statistics lattice results for $\alpha_s$, compare with the three-loop running and extract the value of the flavorless $\Lambda_\ms$ parameter: $ \Lambda_\ms = (303\pm 5 MeV) \frac{a^{-1}(\beta=6.0)}{1.97 GeV}$.