相关论文: Spiral Multi-component Structure in Pade - Approxi…

Pade-approximant treatments of the known terms of the QCD $\beta$-function are seen to develop possible infrared fixed point structure only if the number of fermion flavours is sufficiently large. This flavour threshold is seen to be…

Pade-approximant methods are used to extract information about leading positive zeros or poles of QCD and SQCD beta-functions from the known terms of their perturbative series. For QCD, such methods are seen to corroborate the…

We report our finding of a two scale cut off structure in the infrared nonperturbative dynamics of Pade couplant QCD, in the flavor states $N_{f} \le 8$. We argue that these two NPQCD momentum scales $Q_{c}(Y_{1})$ and $Q_{c}(Y_{2})$ can be…

We address whether Pad\'e-summations of the $\bar{MS}$ QCD $\beta$-function for a given number of flavours exhibit an infrared-stable fixed point, or alternatively, an infrared attractor of a double valued couplant as noted by Kogan and…

A mass scale $\mu_c$ representing the boundary between effective theories of strong interactions and perturbative QCD (infrared and ultraviolet regimes) exists when the $\beta$-function is characterized by a simple pole. This behaviour,…

It has been shown previously that in a relativistic constituent-quark model, predictions for the electromagnetic form factor of the pi meson match not only experimental data but also, in the limit of large momentum transfers, the…

We investigate the infrared structure of QCD within the adiabatic approximation, where soft gluon configurations evolve slowly compared to the fermionic modes. In this formulation, the functional space of gauge connections replaces…

A novel application of the Pade approximation is proposed in which the Pade approximant is used as an interpolation for the small and large coupling behaviors of a physical system, resulting in a prediction of the behavior of the system at…

We investigate the QCD phase diagram as a function of isospin chemical potential at a fixed temperature by directly putting large numbers of \pi^+s into the system. Correlation functions of N \pi^+s systems involves N!N! contractions, and…

The summary of nonperturbative results for the QCD invariant coupling bar{alpha}_s obtained by lattice simulations for functional integral and by solution of approximate Dyson--Schwinger equations reveals a puzzling variety of IR behavior…

We present a specific class of models for an infrared-finite analytic QCD coupling, such that at large space-like energy scales the coupling differs from the perturbative one by less than any inverse power of the energy scale. This…

Perturbative QCD, when optimized by the principle of minimal sensitivity at fourth order, yields finite results for R(e+e-)(Q) down to Q=0. For two massless flavours (n_f=2) this occurs because the couplant "freezes" at a fixed point of the…

The effective interaction between a quark and an anti-quark as obtained previously with by the method of iterated resolvents is replaced by the so called up-down-model and applied to flavor off-diagonal mesons including the pion. The only…

Infrared divergences in the perturbative expansion of gauge theory amplitudes and cross sections have been a focus of theoretical investigations for almost a century. New insights still continue to emerge, as higher perturbative orders are…

We present studies of the SU(2) gauge theory with 4, 6 and 10 fermion flavors. These models are expected to lie on both sides of the edge of the conformal window, where the theory has an infrared fixed point. We observe that the coupling…

The positive zeros of [2|1], [1|2] and the most general possible [2|2] Pade approximants whose Maclaurin series reproduce the presently known terms in the three-flavour QCD beta-function are all shown to correspond to ultraviolet fixed…

The dynamics with an infrared stable fixed point in the conformal window in QCD like theories with a relatively large number of fermion flavors is reviewed. The emphasis is on the description of a clear signature for the conformal window,…

In QCD with 16\half-epsilon massless quark flavours there is an infrared fixed point with alpha_s/pi = (8/321)epsilon in the limit epsilon -> 0+. I develop the idea of Banks and Zaks to expand about N_f=16\half. This expansion is certainly…

If constituent quarks are to emerge from QCD they must have well defined colour and be energetically favoured. After reviewing the general properties of charges in gauge theories, a method for constructing charges is presented and applied…

Using chiral Ward identities of QCD, we derive a relation for the induced pseudoscalar coupling constant which is accurate within a few percent, $g_P = 8.44 \pm 0.16$.