出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：Comparing perturbative and non-perturbative results for renormalization constants has been an issue for a while. The quark mass renormalization constant is a prototype example: discrepancies between different results have been several times ascribed to this issue. Given the logarithmic nature of the divergence, there is no theoretical obstruction to a perturbative computation. The problem, as it is obvious, is how to perform the computation at high loops. Truncation errors should in turn be compared to a variety of errors (e.g. irrelevant effects, chiral extrapolation, finite size) which should be carefully assessed as well. We discuss the status of our computations in Numerical Stochastic Perturbation Theory, in particular for the tree level Symanzik improved gauge action at nf =2. The emphasis is on main goal: how to take all the systematic effects under control at three loop level.
