non-perturbative non-perturbative nonperturbative non-perturbative non-perturbative nonperturbative non-perturbative non-perturbative nonperturbative non-perturbative nonperturbative non-perturbative non-perturbative non-perturbative non-perturbative non-perturbative nonperturbative non-perturbative non-perturbative non-perturbative non-perturbative non-perturbative nonperturbative view article