Related papers: \alpha_S from $F_\pi$ and Renormalization Group Op…
A valid prediction for a physical observable from quantum field theory should be independent of the choice of renormalization scheme -- this is the primary requirement of renormalization group invariance (RGI). Satisfying scheme invariance…
The perturbative expansion of static force and potential is reanalyzed concerning its practical applicability. A well behaved perturbative prediction is given by the integration of the renormalization group equation for the coupling…
One of the largest theoretical uncertainties assigned to the strong coupling constant alpha_s as determined from hadronic tau decays stems from the differences in the results for Fixed Order Perturbation Theory (FOPT), Contour Improved…
We propose a novel renormalization scheme for the hadronic operators. The renormalization factor of the operator in this scheme is normalized by the correlation function at tree level in coordinate space. If we focus on the pseudo scalar…
An updated measurement of alpha_s(m_tau) from ALEPH tau hadronic spectral functions is presented. We report a study of the perturbative prediction(s) showing that the fixed-order perturbation theory manifests convergence or principle…
In the framework of the effective field theory method, we use the experimental data and the perturbative unitarity bounds to determine the values and uncertainty of all the 11 chiral coefficients ($\al_i, i=0, ..., 10$) of the standard…
We formulated the $Lambda(1405)$ (abbreviated as $Lambda^*$) $rightarrow (Sigmapi)^0$ invariant-mass spectra produced in the $K^- + p rightarrow Sigma^+ (1660) + pi^-$, followed by $Sigma^+ (1660) rightarrow Lambda(1405) + pi^+ rightarrow…
We determine $\alpha_s$, $m_c$, and $m_b$ using the relativistic quarkonium sum rule and the renormalization group summed perturbation theory (RGSPT). Theoretical uncertainties, especially originating from the variation of the…
The quantum evolution equations for the field expectation value are analytically solved to cubic order in the field amplitude and to one-loop level in the lambda phi-fourth model. We adapt and use the renormalization group (RG) method for…
Using unitarized Chiral Perturbation Theory methods, we perform a detailed analysis of the $\pi\pi$ scattering poles $f_0(600)$ and $\rho(770)$ behaviour when medium effects such as temperature or density drive the system towards Chiral…
The mean field (MF) approximation for the pion matter, being equivalent to the leading ChPT order, involves no dynamical loops and, if self-consistent, produces finite renormalizations only. The weight factor of the Haar measure of the pion…
We investigate the pion weak decay constant (F_pi) and pion mass (m_pi) at finite density within the framework of the nonlocal chiral quark model from the instanton vacuum with the finite quark-number chemical potential (mu) taken into…
We present a non-perturbative determination of the renormalization factor Z_S of the scalar density in quenched QCD with overlap fermions. Results are obtained at four values of the lattice spacing. By combining Z_S with results for the…
The conventional approach to fixed-order perturbative QCD predictions is based on an arbitrary choice of the renormalization scale, together with an arbitrary range. This {\it ad hoc} assignment of the renormalization scale causes the…
We study the latest $N_f=2+1+1$ and $N_f=2$ ETMC lattice QCD simulations of the nucleon masses and extract the pion-nucleon sigma term utilizing the Feynman-Hellmann theorem in SU(2) baryon chiral perturbation theory with the…
The calculation of perturbative corrections to the spectral moments observable in hadronic $\tau$ decays is reconsidered. The exact order-$\alpha_s^3$ results and the resummation procedure of Le~Diberder and Pich are compared with a partial…
We present an approximation scheme of the nonperturbative renormalization group that preserves the momentum dependence of correlation functions. This approximation scheme can be seen as a simple improvement of the local potential…
The effective potential for the local composite operator $\phi^{2}(x)$ in $\lambda \phi^{4}$-theory is investigated at finite temperature in an approach based on path-integral linearisation of the $\phi^4 $-interaction. At zero temperature,…
Perturbative renormalization group theory is developed as a unified tool for global asymptotic analysis. With numerous examples, we illustrate its application to ordinary differential equation problems involving multiple scales, boundary…
We report our calculation of the pion decay constant $f_\pi$, the axial renormalization constant $Z_A$, and the quenched chiral logarithms from the overlap fermions. The calculation is done on a quenched $20^4$ lattice at $a=0.148$ fm using…