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[en] In this paper we consider a special class of Passarino-Veltman functions which appear during the reduction of the box-type diagrams with infrared divergences and mass singularities. A systematic procedure has been proposed to separate both types of singularities into sthe simplest objects: C0 functions. New JA functions are certain linear combinations of the standard D0 and C0 functions, which are free from all types of singularities, and they have a compact expression in terms of logarithms and dilogarithms. Our results have been numerically compared with the calculations using the well-known package LoopTools.
[en] We derive the effective action of the hard large-x valence charges up to fourth order in their density. Such non-Gaussian weight functionals contribute at leading order in Nc to the connected two-gluon production diagrams that determine di-hadron correlations. The corresponding diagrams are not necessarily (highly) suppressed by the density of valence charges since their infrared divergences differ from those obtained in a Gaussian theory. Therefore, it appears prudent to include such higher dimensional operators when determining initial ensembles for nonlinear evolution of higher n-point functions of Wilson lines.
[en] Euclidean field theories only are considered, with the axial gauge temporal throughout. Pure gauge field models on a lattice are considered. However, the introduction of matter fields would prohibit the trivial elimination of the temporal gauge infrared problem. Results are compared with model calculations. The regularization program is applied to computations
[en] The nonperturbative Schwinger-Dyson equations and Slavnov-Taylor identities of QCD as well as the renormalization group equation are used to obtain the self-consistent behavior of the effective coupling in the infrared region. It is shown that the effective coupling ansatzed solution anti g(q2/μ2,g/sub R/(μ)) = (μ2/q2)/sup lambda/2/g/sub R/(μ) in the infrared limit q2/μ2 → 0 where μ2 is the Euclidean subtraction point; lambda = (d-2)/2 where d is the space-time dimension, can satisfy the above equations if the sufficient self-consistency condition is satisfied. Finally, the nature of the dynamical mass Λ and the 1/N expansion as well as an effective bound-state equation are briefly discussed
[en] Confinement of quarks and gluons in hadrons remains the most important but yet unsolved problem of the modern microscopic theory of strong interactions, QCD. It is well known that confinement is a long-distance (or low-energy) and, therefore, essentially nonperturbative problem of QCD. To solve this problem in a nonperturbative way, the infrared singularities of the chromodynamical Schwinger-Dyson equations for Green's functions are studied. 27 refs
[en] The infrared structure of theories with higher order derivatives is studied through a simple model. It is found that confinement takes place. A formal method which permits one to insert higher order derivatives in Quantum Chromodynamics is presented
[en] The generic Feynman amplitude for a graph G, defined in an earlier paper by an integral over Feynman parameters, is itself a function of regularizing parameters, lambda, ν. The desingularization of the integral which is needed to exhibit the meromorphic structure in these variables is worked out. All ultraviolet and infrared singularities are determined, and these are shown to correspond to certain types of sub and quotient graphs of G, respectively
[en] We consider the Bloch-Nordsieck approximation for quantum chromodynamics and for abelian chromodynamics. In the framework of these models we calculate the infrared asymptotic behavior of the two-point fermion Green function in the axial gauge