相关论文: NSPT estimate of the improvement coefficient $c_A$…
Within the framework of the Schr\"odinger Functional (SF), we outline how to combine Numerical Stochastic Perturbation Theory (NSPT) and PCAC relations to determine the two-loop contributions to the improvement coefficients $c_A$ and…
Numerical Stochastic Perturbation Theory (NSPT) has over the years proved to be a valuable tool, in particular being able to reach unprecedented orders for Lattice Gauge Theories, whose perturbative expansions are notoriously cumbersome.…
Introducing fermionic loops contributions in Numerical Stochastic Perturbation Theory was mainly motivated by the proposal to compute 2-3 loops for renormalization constants (and improvement coefficients). This is feasible because the…
The coefficients multiplying the counterterms required for O($a$) improvement of the action and the isovector axial current in lattice QCD are computed non-perturbatively, in the quenched approximation and for bare gauge couplings $g_0$ in…
We outline a strategy to compute the second-loop contribution to the Csw coefficient of the Sheikoleslami-Wohlert-Wilson fermion action by means of NSPT. We also present preliminary results for higher-order integrators for the Langevin…
By making use of Numerical Stochastic Perturbation Theory (NSPT) we can compute renormalization constants for Lattice QCD to high orders, e.g. three or four loops for quark bilinears. We report on the status of our computations, which…
We calculate the $O(a)$ improvement coefficient for the axial-vector current using the nonperturbative method proposed by the LANL group. Results for the coefficient in the range $\beta=5.93$ to 6.2 are presented. We find $c_A$ is close to…
The treatment of hypercubic lattice artifacts is essential for the calculation of non-perturbative renormalization constants of RI-MOM schemes. It has been shown that for the RI'-MOM scheme a large part of these artifacts can be calculated…
The conservation of the isovector axial current in lattice QCD with massless Wilson quarks is studied to one-loop order of perturbation theory. Following a strategy described in a previous publication, the O($a$) counterterm required for…
First attempts in the application of Numerical Stochastic Perturbation Theory (NSPT) to the problem of pushing one loop further the computation of SU(3) (SU(2)) pertubative beta function (in different schemes) are reviewed and the relevance…
We present results at one-loop order of perturbation theory for various improvement coefficients in on-shell O($a$) improved lattice QCD. In particular we determine the additive counterterm required for on-shell improvement of the isovector…
The Schr\"odinger functional (SF) is a powerful and widely used tool for the treatment of a variety of problems in renormalization and related areas. Albeit offering many conceptual advantages, one major downside of the SF scheme is the…
Using Numerical Stochastic Perturbation Theory (NSPT), we calculate the static self-energy of SU(3) gauge theory up to order \alpha^{20}. Simulations on a large set of different lattice volumes allow for a careful treatment of finite size…
We calculate the $O(a)$ improvement coefficient c_SW in the Sheikholeslami-Wohlert quark action for various improved gauge actions with six-link loops. We employ the conventional perturbation theory introducing the fictitious gluon mass to…
A finite-size technique is employed to compute the normalization constant $Z_A$ of the isovector axial current in lattice QCD. The calculation is carried out in the quenched approximation for values of the bare gauge coupling $g_0$ ranging…
We compute several coefficients needed for O(a) improvement of currents in perturbation theory, using the Brodsky-Lepage-Mackenzie prescription for choosing an optimal scale q*. We then compare the results to non-perturbative calculations.…
The coefficient $c_{\rm sw}$ appearing in the Sheikholeslami-Wohlert improved action is computed to one loop perturbation theory for improved gluon actions including six-link loops. The O($a$) improvement coefficients for the dimension…
We determine quark mass dependent order $a$ improvement terms of the form $b_J am$ for non-singlet scalar, pseudoscalar, vector and axialvector currents, using correlators in coordinate space. We use a set of CLS ensembles comprising…
In previous work, we determined the improvement coefficients $c_\mathrm{V}$ and $c_{\tilde{\mathrm{V}}}$ required for the massless $\mathrm{O}(a)$-improvement of the local and point-split discretizations of the non-singlet vector current…
In general, perturbative expansions of observables in powers of the coupling constant in quantum field theories are asymptotic series. In many cases it is possible to apply resummation techniques to assign a unique finite value to an…